The Round Tower (Rundetaarn), Copenhagen

A royal tower for science and the stars

Completed in 1642 for King Christian IV, the Round Tower was conceived as the astronomical heart of Copenhagen, part of the larger Trinitatis complex that united church, library and observatory in one ambitious project. From the outset it was a working scientific facility, giving scholars a stable, elevated platform from which to chart the night sky above the city’s rooftops. That scientific role lives on today. The observatory near the summit is one of the oldest functioning observatories in Europe, traditionally opening on selected evenings in the cooler months. Inside its distinctive copper dome, astronomers guide visitors through the planets and star fields, continuing a tradition of curiosity that has spanned nearly four centuries.

The famous spiral ramp and ascent

Instead of a staircase, most of the climb is via a broad, cobbled spiral ramp that coils 7½ times around the tower’s hollow core. Originally designed wide enough for horses and carriages to reach the top with heavy instruments and books, it now offers a gradual, almost theatrical approach as you circle higher above the streets of the old town. Along the way, small alcoves and lookouts break the ascent, offering glimpses through narrow windows to tiled roofs and spires. Near the top, the ramp gives way to a broad wooden staircase and then a tighter stone stair, a final reminder that the last stretch of the journey still demands a short, steeper climb before you emerge into daylight on the upper platform.

Library Hall: from university stacks to cultural stage

Roughly halfway up, the Library Hall occupies a generous floor above the adjoining church. Once home to the university’s book collection, it stored thousands of volumes in the days when this was Copenhagen’s main academic library. The high, white‑washed vaults and timber floor were built to carry both weight and quiet concentration. Today the hall has a very different life. It hosts changing exhibitions, from contemporary art to historical displays, as well as concerts, talks and special events. A small shop and café counter make it a natural pause in the climb, with space to sit beneath the arches and appreciate how the tower still balances learning, culture and everyday city life.

A panorama of spires and rooftops

At the summit, an open‑air viewing platform circles the tower, ringed by a simple iron balustrade. From here, Copenhagen reveals itself in all directions: the copper and brick spires of churches, the outline of Rosenborg Castle in the distance, and on clear days the shimmer of the Øresund and the coast of Sweden. The height is modest by modern standards, but the central location makes the view feel intimate rather than remote. You look out across the city’s historic core at almost eye level with nearby towers, tracing medieval streets and modern boulevards from a single, compact vantage point.

Living landmark in the heart of the city

Despite its age, the Round Tower functions less as a static monument and more as a living part of Copenhagen’s cultural calendar. Exhibitions rotate through the Library Hall, seasonal astronomy evenings bring the observatory to life, and occasional thematic programmes focus on topics like light, time and the universe. Ongoing restoration work on the copper dome and observatory underscores its status as protected heritage. Rather than closing it off from everyday use, conservation aims to keep Christian IV’s "star castle" active for future generations, preserving both the brickwork beneath your feet and the view of the sky above your head.

Practical experience and accessibility

A visit to the Round Tower is compact but layered: most guests spend one to two hours exploring the ramp, Library Hall, viewing platform and, when open, the observatory. The ramp’s 200‑metre incline is gentle but continuous, and the final staircases mean full access to the top is not suitable for wheelchairs or those who struggle with steps. Information panels explain the tower’s history, scientific role and architecture, while the central location on Købmagergade makes it easy to combine with nearby museums, churches and shopping streets. Inside, the rule is simple: look up, slow down and let the spiral pull you through centuries of Copenhagen history in a single, graceful ascent.