Bagågraven & Pyritsøen Coastal Clay Pit

From working clay pit to wild coastal hollow

Bagågraven sits tucked between forest, coast and the Hasle–Rønne stretch of shoreline, where the Baltic rolls in against steep man‑made slopes. Around 1900 clay extraction began here, feeding the Hasle tile and refractory works that lined the coast. For decades, machines bit steadily into the shoreline, carving a broad amphitheatre‑like hollow that has since partly filled with water to form Pyritsøen, a sheltered lake just inland from the sea. When extraction stopped in the late 1980s, the site was left as a raw wound in the landscape. Over time, wind, rain and the Baltic have reshaped the exposed clay and sand, softening edges and cutting small ravines. The result is an unusual semi‑wild bowl of slopes, ponds and banks, framed by low woodland and opening westwards to the horizon.

Layers from the Jurassic beneath your feet

Bagågraven exposes deposits known as the Bagå Formation, laid down in the Middle Jurassic around 170 million years ago. In the scarred walls you can see a sequence of dark coal‑bearing clays, pale sandstones and grey muds, once formed in river channels and floodplains on a broad delta. Between the channels, quieter water deposited fine clay while vegetation colonised the low‑lying ground. Nearby, at the coast around Pyritsøen, geologists have found dinosaur footprints preserved in sandstone blocks washed out of these layers. They are some of the key pieces of evidence that large dinosaurs once roamed Bornholm, which remained dry land while most of future Denmark lay under shallow seas. Standing here, it is easy to picture broad‑backed animals trudging across a muddy delta long before the Baltic existed.

A refuge for birds, amphibians and coastal plants

After the diggers left, Bagågraven quickly became a refuge for wildlife. The steep faces and loose material attracted sand martins and other burrowing birds, while shallow pools and the lake margins turned into breeding grounds for frogs and toads. The mixture of bare ground, scrub and wet patches is also good insect habitat, and sharp‑eyed visitors may notice dragonflies skimming low over the water in summer. Closer to the sea, hardy coastal plants push roots into the eroding banks and pebble‑strewn foreshore. Storms periodically bite into the protective ridge between Pyritsøen and the open Baltic, carrying clay and sand away and slowly altering the outline of the coast. It is a landscape in visible motion, where each winter’s waves redraw the fine details of the shoreline.

Short walks, viewpoints and quiet pauses

For visitors, Bagågraven is a compact, low‑key destination rather than a formal park. Unmarked paths and trods loop around the hollow, linking forest, lake edge and seafront. From the upper banks you gain broad views along Bornholm’s west coast towards Rønne and, in clear light, north towards Hasle’s smoking chimneys and cliffs. Down by the water, the atmosphere shifts. The lake surface often lies calmer than the sea beyond, reflecting sky and banks, while the muffled boom of surf reaches you from the far side of the narrow land bridge. It is an easy place to linger on a bench or rock, watching the changing light and the movement of clouds above the Baltic.

A stop on coastal trails and cycle routes

Bagågraven also functions as a natural pause point on longer excursions. The coastal trail that connects Rønne and Hasle passes close by, weaving between forest and sea. Cyclists on the popular Hasle–Rønne route skim the land bridge and can detour a few minutes to look down into the former pit and across Pyritsøen. There are no attractions in the theme‑park sense here: no displays, no playgrounds, simply a raw, evolving landscape shaped first by industry and now by wind and waves. That simplicity is part of its charm. Bagågraven offers a compact encounter with Bornholm’s deep time, its coastal energy and its quieter, everyday nature, all within a short outing.