The Round Tower

The Round Tower is one of the most delightful buildings in Copenhagen and one of the cheapest big sights in the city. King Christian IV had it built as part of the Trinitatis Complex, which combined a student church, a university library and an astronomical observatory in one ambitious project; the foundation stone was laid on 7 July 1637 and the tower was finished in 1642. It is a stout brick cylinder about 35 metres tall on Kobmagergade, in the heart of the old town, and its great surprise is inside: instead of a staircase, a broad, cobbled spiral ramp winds seven and a half times around the hollow core of the tower, more than 200 metres in all, up to the observation platform at the top. The ramp was built so that a horse and carriage could carry heavy instruments up to the observatory, and the most famous story about it is that Tsar Peter the Great rode a horse to the top in 1716, with the empress following in a carriage. Halfway up, a door opens into the Library Hall, the old university library above the church, now a light, vaulted space with changing exhibitions, concerts and talks, plus a small shop and cafe. At the top, the viewing platform gives a 360-degree view over the red-tiled roofs and copper spires of the old town, with Christiansborg, the City Hall tower and, on a clear day, the bridge to Sweden in the distance. The observatory itself, the oldest functioning observatory building in Europe, has just been restored: King Frederik X reopened it in August 2026, opening the dome himself during a partial solar eclipse, and the tower returned fully to visitors in October 2026. In winter, the astronomers open the telescope to the public on selected evenings. Entry costs about 60 DKK for adults and is free for under-18s, and the tower is open daily, until late in summer.

The tower is full of Christian IV's personality. The king was fascinated by astronomy, partly because of the legacy of the Danish astronomer Tycho Brahe, and the observatory was meant to continue his work in the capital. On the facade facing the street, a golden rebus, a puzzle of letters and symbols said to have been sketched by the king himself, asks God to guide learning and justice into the heart of the crowned King Christian IV. The church below, Trinitatis Church, is still in use and well worth a look, and the old university library above it held the country's most important collections until a great fire in 1728 destroyed many of them. Today the tower is run as a small cultural institution, with exhibitions on its history and on astronomy as well as art and design shows in the Library Hall.

How to visit well: the climb is gentle, as the ramp rises slowly, and most people reach the top in ten to fifteen minutes with stops, so it suits children and older visitors who would struggle with a steep staircase; the last few metres to the platform are a short, narrow stair. Look for the toilet installed in the wall halfway up, a historic curiosity, and the glass floor over the hollow core. Go late in the afternoon for the light over the rooftops, or in the evening in summer, when the tower stays open late. In winter, check the schedule for the evening observatory sessions, when the astronomers show the planets through the large telescope; on selected summer Sundays, they show the sun through a protective filter.

The Round Tower sits on Kobmagergade, between Stroget and the Latin Quarter, so it fits naturally into a walk through the old town. Combine it with the student quarter around the university and the cathedral, with Rosenborg and the King's Garden ten minutes away, or with Torvehallerne for lunch. It is closed on 24 and 25 December and 1 January and closes early on 31 December, and the Copenhagen Card includes admission, but at this price the tower is good value for everyone.