Porth yr Ogof – Wales’ Largest Cave Entrance
Step into Wales’ largest cave entrance, where the Afon Mellte vanishes underground in the heart of the Brecon Beacons’ Waterfall Country.
Porth yr Ogof, near Ystradfellte in the Brecon Beacons National Park, is home to Wales’ largest cave entrance, where the Afon Mellte river vanishes underground. The imposing 20m-wide portal opens into a maze of limestone passages, underground streams and waterfalls, making it a classic training ground for cavers. While the entrance chamber is accessible to visitors in dry weather, the full system is a serious caving destination, best explored with experienced guides. The surrounding Waterfall Country offers scenic walks and dramatic gorges.
A brief summary to Porth yr Ogof
- Aberdare, Ystradfellte, CF44 9JF, GB
- Visit website
- Duration: 0.5 to 3 hours
- Budget
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Outdoor
- Mobile reception: 3 out of 5
- Monday 12 am-12 am
- Tuesday 12 am-12 am
- Wednesday 12 am-12 am
- Thursday 12 am-12 am
- Friday 12 am-12 am
- Saturday 12 am-12 am
- Sunday 12 am-12 am
Local tips
- Check river levels and weather before visiting; the cave can flood rapidly after rain, making it extremely dangerous.
- Wear sturdy, grippy footwear – the path down and the cave floor are rocky and slippery, especially when wet.
- Bring a torch if you plan to go inside the entrance chamber; daylight fades quickly, and the floor is uneven.
- Heed all warning signs – the resurgence pool is deceptively deep and fast-flowing; only experienced cavers with proper gear should attempt to cross it.
- Combine your visit with the nearby Four Falls Trail or other Waterfall Country walks for a full day in the Brecon Beacons.
For the on-the-go comforts that matter to you
- Restrooms
- Drinking Water
- Seating Areas
- Information Boards
- Visitor Center
Getting There
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Car
From the A465 Heads of the Valleys Road, follow signs for the Waterfalls Information Centre near Pontneddfechan, then continue towards Ystradfellte to the pay-and-display car park at Cwm Porth. The drive from Pontneddfechan takes about 15–20 minutes on narrow, winding roads; parking costs a few pounds for several hours.
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Public Transport + Walk
Take a train to Neath or Merthyr Tydfil, then a local bus to Pontneddfechan or Ystradfellte. From there, it’s a 3–4 km walk along country roads and paths to the Cwm Porth car park and cave entrance, taking about 45–60 minutes on foot.
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Guided Caving Tour
Several outdoor centres in the Brecon Beacons offer guided caving trips into Porth yr Ogof, including equipment and expert leadership. These typically last half a day and cost around 40–60 GBP per person, suitable for beginners with some fitness.
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Walking from Ystradfellte
From the village of Ystradfellte, follow footpaths and country lanes for about 3 km to the Cwm Porth car park. The walk takes roughly 45 minutes on mixed terrain, with some steep sections and uneven surfaces.
Porth yr Ogof location weather suitability
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Any Weather
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Rain / Wet Weather
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Clear Skies
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Mild Temperatures
Discover more about Porth yr Ogof
Gateway to the Underground
Standing before Porth yr Ogof, you face what is widely regarded as the largest cave entrance in Wales: a vast, arched opening nearly 20 metres wide and several metres high, carved by the Afon Mellte through Carboniferous limestone. The river’s name, meaning 'lightning', hints at its nature – a flashy, rain-fed stream that can transform from a gentle flow to a raging torrent in hours. In normal conditions, a dry riverbed leads into the day-lit entrance chamber, where daylight still reaches deep into the cave, but after heavy rain, water floods the passage, making it impassable and extremely dangerous.A Cave for Cavers
The full Porth yr Ogof system extends over two kilometres with multiple entrances and a complex network of passages, streams, sumps and waterfalls. It is no longer a commercial showcave but is instead used as a training and introduction cave for caving clubs, schools and outdoor centres. Key features include the Wormhole, Letterbox and Creek passages, as well as the Inner Sanctum and Waterfall Series, all requiring proper caving gear, experience and often a guide. The resurgence pool, where the river re-emerges, is particularly hazardous and has been the site of several tragic incidents, underscoring that this is not a casual tourist cave beyond the entrance zone.Geology and Landscape
Porth yr Ogof lies in the heart of Waterfall Country, where rivers draining the Old Red Sandstone hills cut steep gorges through bands of Carboniferous limestone. The cave is a classic karst feature, formed by the dissolution of limestone by slightly acidic water over millennia. The area is protected as a Site of Special Scientific Interest and Special Area of Conservation, recognised for its geological and ecological value. The surrounding woodland and gorges, with their ferns, mosses and waterfalls, create a magical, almost primeval atmosphere that has even drawn film crews looking for otherworldly locations.Visiting the Entrance
For most visitors, the experience is about standing in the immense entrance chamber, feeling the cool, damp air, hearing the river’s rush and seeing how the landscape literally disappears underground. A short, steep descent from the Cwm Porth car park and visitor area leads down to the river and the cave mouth. In dry weather, it is possible to walk a short way inside with a torch, but there is no formal path, and the floor is rocky, slippery and uneven. Warning notices clearly state that only properly equipped and experienced cavers should venture further, and the resurgence pool should never be crossed without specialist training and equipment.Access and Safety
The cave is managed by the Brecon Beacons National Park Authority, with a pay-and-display car park and basic visitor facilities nearby. Parking is available at Cwm Porth, close to the Waterfalls Information Centre in Pontneddfechan, and the site is well signed from the A465 and A4059 roads. While the entrance is open year-round, conditions change rapidly with the weather; what is a safe walk one day can become a life-threatening situation after rain. Visitors are strongly advised to check river levels and weather forecasts, wear sturdy footwear, and never enter the cave alone or without proper preparation if planning any exploration beyond the entrance.Iconic landmarks you can’t miss
YHA Brecon Beacons
11.0 km
Rustic farmhouse hostel offering clean, cozy accommodation and a warm communal atmosphere in the heart of Brecon Beacons National Park.
Cantref - Adventure Farm in South Wales
18.5 km
Experience family fun at Cantref Adventure Farm in South Wales, where children can connect with animals and enjoy exciting outdoor activities.
Aberfan Disaster Memorial
18.7 km
Explore the Aberfan Disaster Memorial, a poignant tribute to resilience and remembrance in the heart of Wales, honoring lives lost in the 1966 tragedy.
Theatr Brycheiniog
19.6 km
Experience the vibrant performing arts scene at Theatr Brycheiniog in Brecon, where culture meets scenic beauty along the canal.
Brecon Canal Basin
19.7 km
Breathe in the beauty of Brecon Canal Basin, a serene escape in Wales perfect for leisurely walks, local cuisine, and outdoor adventures amidst stunning landscapes.
The Promenade
19.8 km
Discover tranquility and natural beauty at The Promenade in Brecon, a perfect park to unwind and enjoy the stunning Welsh landscape.
Gate Gallery & Glassworks
19.8 km
Discover the artistic beauty of handmade glassware at Gate Gallery & Glassworks in Brecon, where craftsmanship meets creativity.
Parc Bryn Bach
19.8 km
Experience the natural beauty and recreational fun of Parc Bryn Bach in Tredegar, a perfect destination for outdoor enthusiasts and families.
Y Gaer Museum, Art Gallery & Library
19.8 km
Explore Y Gaer Museum, Art Gallery & Library in Brecon for an enriching experience of local history, art, and literature in a cultural landmark.
Duke of Wellington Monument
19.8 km
Historic bronze statue honoring the Duke of Wellington, a commanding presence in Brecon’s town centre and a testament to local artistry and British heritage.
Brecon Town Tours - guided history walks
19.8 km
Experience the rich history of Brecon with guided tours that unveil the town's hidden gems and captivating stories in the heart of the Brecon Beacons.
Brecon Barracks
19.8 km
Historic military hub in Brecon, home to the Royal Welsh Regiment and its museum, set within the stunning Brecon Beacons National Park.
The Brecon Castle Hotel
19.8 km
Historic Wales’ oldest hotel blending timeless charm with modern comforts near Brecon Beacons National Park.
Brecon Walk Way
19.8 km
Experience the tranquility and stunning landscapes at Brecon Walk Way, a must-visit tourist attraction in the heart of Wales.
The Royal Welsh Regimental Museum
19.9 km
Explore the Royal Welsh Regimental Museum in Brecon, where Wales' military history comes alive through captivating exhibits and rich heritage.
Unmissable attractions to see
Four Waterfalls Walk
1.3 km
Discover the enchanting Four Waterfalls Walk, a scenic 9 km trail through ancient woodland and cascading falls in Wales’ Brecon Beacons National Park.
Sgwd Clun-Gwyn Waterfall
1.6 km
Discover the cascading beauty of Sgwd Clun-Gwyn, a serene multi-step waterfall nestled in the lush woodlands of South Wales’ Brecon Beacons.
Sgwd Isaf Clun-Gwyn
1.9 km
Discover the serene multi-tiered cascades of Sgwd Isaf Clun-Gwyn, a tranquil jewel on the Four Waterfalls Walk in Wales’ Brecon Beacons.
Sgwd y Pannwr
2.2 km
Discover the serene tiered cascade of Sgwd y Pannwr, a scenic highlight of the Four Waterfalls Walk in Wales’ Brecon Beacons National Park.
Sgwd Yr Eira Waterfall
2.5 km
Walk behind the stunning 50-foot curtain of water at Sgwd yr Eira, the enchanting Waterfall of Snow in Wales’ Brecon Beacons.
Sgwd Gwladys Waterfall
4.5 km
Discover the serene beauty of Sgwd Gwladys, a graceful 7-meter waterfall nestled in Wales’ scenic Waterfall Country.
Penderyn Brecon Beacons Distillery - Visitor Centre and Shop
4.8 km
Discover the home of Welsh whisky in the Brecon Beacons – tour the original Penderyn Distillery, see the Faraday still, and taste award-winning single malts.
Dinas Rock
4.8 km
Explore the towering limestone cliffs, ancient hillfort, and enchanting waterfalls of Dinas Rock in the heart of Wales’ Waterfall Country.
Cadair Fawr
5.0 km
Accessible mountain views across South Wales' rolling landscape, perfect for all abilities.
Waterfall Country
5.5 km
Discover the enchanting cluster of waterfalls and ancient woodlands in Wales’ Brecon Beacons National Park, where rivers carve dramatic gorges.
Sgwd Gwladys
5.6 km
Discover the enchanting 7-meter cascade of Sgwd Gwladys, a legendary waterfall nestled in South Wales’ scenic Waterfall Country.
Fforest Fawr Geopark
5.8 km
Explore Fforest Fawr Geopark’s ancient geology, wild landscapes, and rich Welsh heritage in the heart of the Brecon Beacons National Park.
Maen Llia
6.7 km
Discover Maen Llia, a majestic Bronze Age standing stone in the Brecon Beacons, steeped in legend, celestial alignments, and prehistoric mystery.
Ogof Ffynnon Du National Nature Reserve
7.1 km
Explore the UK’s deepest cave beneath wild moorlands and historic ruins in the breathtaking Ogof Ffynnon Ddu National Nature Reserve.
Henrhyd Falls
7.5 km
Discover South Wales’ tallest waterfall with a thrilling walk behind the cascading curtain at Henrhyd Falls in the Brecon Beacons.
Essential places to dine
The Red Lion Inn, Penderyn
4.3 km
A cozy Welsh gastropub blending traditional charm, local flavors, and legendary roasts in the scenic village of Penderyn.
Penycae Inn Ltd
8.5 km
Cozy gastropub in the heart of South Wales offering fine Welsh cuisine, scenic mountain views, and a unique family-friendly atmosphere.
Carnivore By The Mine
9.3 km
A cozy meat-lover’s haven in Neath, blending hearty dishes with heartfelt mining heritage and warm local charm.
Abercrave Inn
10.3 km
A rustic Welsh country inn offering hearty home-cooked meals, cozy charm, and a peaceful rural retreat in Abercraf.
Mango House Restaurant
11.2 km
Experience authentic Indian cuisine with warm hospitality in the heart of Merthyr Tydfil’s Cefn-coed-y-cymmer.
Aberglais Inn
11.8 km
Cozy pub and restaurant in Merthyr Tydfil offering hearty British classics, vegan and gluten-free options, with a warm, friendly atmosphere.
Red Cow Inn
12.9 km
A charming traditional Welsh pub in Pontsticill offering hearty home-cooked meals, award-winning ales, and a warm, welcoming atmosphere.
Rhydycar Harvester
14.0 km
Casual family dining with classic British flavors and welcoming amenities in Merthyr Tydfil’s Rhydycar Leisure Park.
The Pantyscallog Inn
14.1 km
A beloved steakhouse in Pant, Merthyr Tydfil, known for hearty portions, friendly service, and a warm, welcoming atmosphere.
The Tai’r Bull Inn
15.1 km
A cosy Welsh country pub and B&B offering hearty fare, real ales, and warm hospitality in the heart of Brecon Beacons National Park.
The Tanners Arms
15.2 km
Rustic Welsh pub and cozy B&B nestled in scenic Defynnog, offering hearty food, local ales, and warm hospitality near the Brecon Beacons.
Pentrebach House Table Table
15.8 km
Classic British pub dining with family-friendly charm and hearty meals in the heart of Merthyr Tydfil.
Usk & Railway Inn
16.3 km
Cozy country inn with hearty local cuisine and premium comfort near Brecon Beacons National Park.
The White House
16.8 km
A charming country inn near Brecon Beacons offering warm hospitality, fresh local cuisine, and cozy rooms for a relaxing Welsh getaway.
Castle Coaching Inn
17.3 km
Historic Welsh inn in Trecastle offering cozy rooms, traditional cuisine, and warm hospitality near Brecon Beacons National Park.
Markets, malls and hidden boutiques
Kindle House
14.2 km
Whimsical Victorian boutique where curated rooms and creative collections inspire joy and discovery.
The UK Loose Leaf Tea Company Ltd
18.4 km
Discover ethically sourced, premium loose leaf teas and sustainable brewing essentials at The UK Loose Leaf Tea Company Ltd in Brecon.
Hay & Brecon Farmers Brecon
18.6 km
Experience the best of local Welsh produce at Hay & Brecon Farmers Brecon, where freshness and quality meet a warm community spirit.
B&M Home Store with Garden Centre
18.8 km
Affordable shopping meets gardening passion at Brecon’s versatile B&M Home Store with Garden Centre.
Mind
19.0 km
Explore unique finds and support mental health initiatives at Mind Charity Shop in Brecon, where every purchase makes a difference.
CERTAS - BRECON
19.3 km
Discover convenience in Brecon with CERTAS, your one-stop shop for essentials, local treats, and friendly service.
Kitty Keane's Vintage
19.8 km
Discover authentic Welsh vintage and handcrafted treasures at Kitty Keane's Vintage, a charming craft shop in the heart of Brecon.
DIXIES CORNER
19.8 km
Brecon's trusted specialist in authentic military surplus and outdoor gear since establishment.
Bentley & Co Home Interiors & Coffee Shop
19.8 km
Discover stylish home interiors and savor homemade coffee and light lunches in the heart of Brecon’s charming Ship Street.
Bi Ped Cycles
19.8 km
Biped Cycles: Your expert cycling partner in Brecon, offering quality bikes, certified e-bike servicing, and personalized care near the Brecon Beacons.
Dressed To Impress!
19.8 km
Family-run bridal and occasion wear boutique in Brecon offering elegant dresses and personalized service for all body types.
Gibb Outdoors
19.8 km
Trusted outdoor gear and expert advice in the heart of Brecon for all your Welsh adventures.
Beacons Antiques
19.8 km
Discover timeless vintage treasures and unique collectibles at Beacons Antiques, a charming hub of history in the heart of Brecon.
Premier
19.8 km
Your friendly, convenient stop for groceries and essentials in the heart of Brecon, open early to late every day.
Ardent Gallery
19.8 km
Explore contemporary art at Ardent Gallery in Brecon, a vibrant hub for creativity and cultural expression.
Essential bars & hidden hideouts
Drovers Arms
19.1 km
A welcoming Welsh village pub blending historic charm with hearty fare and friendly hospitality in the heart of Llanfaes, Brecon.
The Three Horseshoes Inn
19.4 km
A cosy Welsh village pub blending traditional charm with refined British cuisine and a warm, welcoming atmosphere.
hop in beer and gin
19.8 km
Discover Brecon’s quirky bar with top-quality craft beers, artisanal gins, and delicious tapas in a cozy, historic setting.
The Rorkes Drift
19.8 km
Historic Welsh pub in Brecon offering local ales, lively music, and a warm atmosphere inspired by the legendary Rorke’s Drift battle.
The Sarah Siddons
19.8 km
Experience authentic Welsh hospitality with local ales and lively atmosphere at The Sarah Siddons, Brecon’s beloved town centre pub.
The Lounge Bar & Cafe
19.9 km
Brecon’s pioneering bar with a modern twist, offering signature cocktails, live music, and a welcoming atmosphere in the town centre.
Markets Tavern
19.9 km
Traditional Welsh pub and welcoming hotel in Brecon offering hearty food, cozy rooms, and authentic local charm on Free Street.
Shoemakers Arms
20.6 km
Charming community-run pub in the heart of Brecon Beacons, offering warm hospitality and authentic Welsh cuisine in a rustic setting.
Royal Oak
20.7 km
Cozy Welsh pub in Pencelli offering traditional hospitality and local ales amidst the scenic Brecon Beacons.
The Star Inn
21.1 km
A cozy and characterful pub with quality food and a sunny beer garden in the heart of Talybont-on-Usk, perfect for walkers and families alike.
The Dyffryn Arms
21.9 km
A classic Welsh pub in Neath offering hearty meals, warm hospitality, and a welcoming atmosphere for locals and visitors alike.
Pontardawe Inn
22.1 km
Lively, dog-friendly pub in Pontardawe offering hearty food, real ales, live music, and a warm Welsh welcome in a cozy setting.
Coach & Horses
22.9 km
Historic canal-side pub and inn in Llangynidr offering hearty Welsh fare, cozy rooms, and a warm, welcoming atmosphere.
The Pwllgloyw Arms
23.5 km
A cozy mountain pub in Powys offering hearty Welsh fare, local ales, and a warm, welcoming atmosphere year-round.
The Pennsylvania
23.7 km
A welcoming traditional pub on Briton Ferry Road, The Pennsylvania offers a classic Welsh community gathering spot with a friendly and relaxed atmosphere.
Nightclubs & after hour spots
The Kirkhouse Nightclub (Koolers)
13.2 km
Experience the vibrant and friendly nightlife of Merthyr Tydfil at The Kirkhouse Nightclub, known locally as Koolers.
Pure Bar & Nightclub Ltd
13.6 km
A lively nightclub and cocktail bar in Merthyr Tydfil offering vibrant music, crafted drinks, and late-night entertainment in South Wales.
The Top Club
19.5 km
Experience Blaengarw’s vibrant nightlife at The Top Club, where electrifying entertainment meets community spirit in the heart of South Wales.
Northcote Conservative Club
19.8 km
Discover the lively ambiance of Northcote Conservative Club, Brecon's premier destination for nightlife, music, and local culture.
Brecon Working Mens Club
19.8 km
Experience authentic Welsh hospitality at Brecon Working Mens Club, where locals gather for drinks and camaraderie in a charming setting.
BRECON JAZZ
19.8 km
Experience the soulful sounds of Brecon Jazz, an intimate venue celebrating the rich heritage of jazz music in the heart of Wales.
Brecon Jazz Club (Muse Arts Centre)
19.8 km
Discover the heart of jazz in Brecon at the Brecon Jazz Club, where live music and a vibrant atmosphere collide for an unforgettable night.
The Arch Bar & Nightclub
23.2 km
A lively Neath hotspot blending nightclub energy, live music, pub charm, and Thai cuisine in one vibrant venue.
Squares Night club
23.3 km
Experience Porth’s vibrant nightlife at Squares Nightclub, where music, dance, and unforgettable evenings come alive every weekend.
Jimmy's Bar
27.8 km
Experience the vibrant nightlife and live music scene at Jimmy's Bar, Port Talbot’s lively local hotspot with a welcoming atmosphere.
Eclipse Nightclub
28.4 km
Experience Pontypridd’s vibrant midweek nightlife at Eclipse Nightclub, where music, dancing, and community come alive every Wednesday night.
Popworld - Swansea
33.3 km
Experience Swansea’s energetic retro nightclub with affordable cocktails, themed events, and a lively dance floor in the heart of the city.
PlanB
33.6 km
Swansea’s energetic two-floor nightclub with a focus on dance music, lively DJs, and great drink deals for a night to remember.
Cuba Escape
33.6 km
Experience Swansea’s vibrant nightlife at Cuba Escape, where live music, energetic crowds, and a colorful atmosphere come together for unforgettable nights.
Sin City
33.9 km
Energetic Swansea nightclub with live music, affordable drinks, and a lively atmosphere on Dillwyn Street.
For the vibe & atmosphere seeker
- Adventurous
- Unique
- Scenic
- Tranquil
For the architecture buff
- Historic
- Landmarks
- Parks & Gardens
- Heritage Neighborhoods
For the view chaser and sunset hunter
- Iconic Views
- Panoramas
For the social media creator & influencer
- Instagrammable
- Photo Spots
- Selfie Spots
- Aesthetic Corners
For the eco-conscious traveler
- Protected Area
- Nature Reserve
- National Park
- Public-Transport Accessible
- Leave-No-Trace Critical
- Locally Managed
For the kind of experience you’re after
- Cultural Heritage
- Photowalk
- Nature Escape
- Day Trip
- Weekend Getaway
For how adventurous you want the journey to be
- Easy Access
- Requires Hike
Location Audience
- Family Friendly
- Senior Friendly
- Child Friendly
- Teen Friendly
- Solo Friendly
- Couple Friendly
- Solo Female Friendly
- Business Friendly