Slotsholmen – Castle Island at Copenhagen’s Heart

Castle Island where Copenhagen began

Slotsholmen, literally “Castle Islet,” sits in the middle of Copenhagen’s harbour, wrapped in a ring of green-brown canals that clearly mark it out from the surrounding streets. Long before the city became a modern capital, this low island of sandbanks and shoals was chosen in 1167 by Bishop Absalon as the place to build a fortified castle, protecting trade on the Øresund and anchoring a small harbourside settlement that grew into Copenhagen. Over the centuries the original stronghold was attacked, demolished, rebuilt and expanded, but the idea of Slotsholmen as the country’s centre of power never shifted. Walking onto the island today, it is hard to imagine those early timber palisades and stone keeps. Yet beneath your feet in the ruins under Christiansborg Palace lie the foundations of Absalon’s fortress and later Copenhagen Castle, a subterranean timeline of walls and vaulted cellars that show how the island’s role evolved from frontier outpost to royal residence. Above ground, the stone bridges that now connect Slotsholmen to the rest of the city emphasize how this small island has always been both apart from, and central to, Copenhagen’s story.

Christiansborg Palace and the machinery of state

The dominant presence on Slotsholmen is Christiansborg Palace, the latest in a series of grand palaces that have risen and fallen on this same footprint. Fire repeatedly destroyed earlier buildings, and what you see now is largely an early 20th‑century palace, designed to house the institutions of a constitutional monarchy rather than a single royal household. Inside its granite and copper-clad exterior sit the three pillars of Danish democracy: the Parliament chamber, the Supreme Court and the offices of the Prime Minister, all sharing the same sprawling complex. For visitors, the palace is more than a symbol. State reception rooms lined with tapestries and chandeliers, the Royal Stables with ceremonial horses and carriages, and the excavated ruins beneath the building can all usually be visited on separate tickets or combined passes. High above, the Christiansborg Tower rises as one of the best urban viewpoints in Copenhagen, offering sweeping panoramas over spires, rooftops and the harbour. It is a striking contrast: medieval foundations below, modern politics in the middle, and open sky at the top.

Historic institutions beyond the palace walls

Slotsholmen’s importance is not confined to Christiansborg. On the island’s waterfront edge sits the Royal Library complex, where a sober 19th‑century reading room adjoins the striking modern “Black Diamond” addition across the canal. Inside, hushed spaces and rows of books underscore the island’s role as a guardian of Danish knowledge and culture. Elsewhere, the Danish War Museum occupies the former arsenal, its long brick halls recalling the days when ships and cannon dominated national defence. Another prominent landmark is the old Stock Exchange, with its distinctive twisted spire of intertwined dragon tails. Built in the 17th century under King Christian IV, it embodies the era when trade and naval power were shaping Denmark’s fortunes. Nearby, Thorvaldsens Museum, dedicated to the neoclassical sculptor Bertel Thorvaldsen, adds an artistic note with colourful façades and serene courtyards. Government ministries, courts and offices fill many of the remaining buildings, giving the island a working weekday rhythm as civil servants and politicians cross cobbled squares between meetings.

Canals, courtyards and everyday life

Despite its dense concentration of institutions, Slotsholmen is surprisingly walkable and human in scale. Narrow pavements follow the course of the Slotsholmen Canal, where sightseeing boats glide past reflecting façades and low stone quays provide close-up views of the water. In fine weather, locals and visitors linger on benches and low steps, watching the play of light on the canal and the slow traffic of bicycles back on the mainland streets. Within the island, courtyards such as the Parliament courtyard and open squares around the palace create pockets of calm away from the harbour breeze. Here you notice details you might otherwise miss: equestrian statues of past monarchs, ornate lampposts, coats of arms carved above gateways. Although security measures are visible around some buildings, Slotsholmen retains an open, civic character, inviting you to wander between culture, government and history without clear boundaries.

Exploring Slotsholmen as a visitor

For travellers, Slotsholmen works well as both a dedicated half‑day visit and a backdrop to wider explorations of central Copenhagen. You can spend a focused morning visiting the palace ruins, reception rooms and tower, then cross to the Royal Library or Thorvaldsens Museum in the afternoon. Alternatively, you can simply loop the island on foot, appreciating the changing views of façades and canals, then return another day to explore interiors in more detail. Most of the main attractions on the island charge individual admission fees, while strolling the canals, courtyards and exterior spaces remains free. The area is largely flat and paved, though cobblestones in some courtyards can be slightly uneven. Even without going inside any building, Slotsholmen gives a strong sense of continuity: from Bishop Absalon’s first castle through absolute monarchy, naval expansion and the move to constitutional rule, the island has continuously adapted while keeping its position at the centre of Danish public life.