The Round Tower

A Royal Vision Cast in Stone

The Round Tower stands as one of Copenhagen's most recognizable landmarks, erected in 1642 by King Christian IV as part of the ambitious Trinitatis Complex. The cornerstone was laid on July 7, 1637, and five years later the tower was completed as the first of three interconnected structures designed to house an observatory at the summit, a university library on the floor above Trinity Church, and the church itself below. This architectural ensemble reflected Christian IV's passion for both scientific advancement and royal grandeur, positioning Denmark at the forefront of European astronomical observation during the 17th century.

The Spiral Ramp: Engineering Marvel and Visitor Experience

The tower's most distinctive feature is its famous spiral ramp, which winds 7½ times around the tower's hollow core—a design unique in Denmark. Stretching approximately 200 metres from the entrance on Købmagergade to the upper stairs, this gently ascending passage was originally designed to allow horse-drawn carriages to reach the observatory level, a practical consideration reflecting the tower's multifunctional purpose. Today, the ramp remains the only route to the summit, offering visitors a meditative ascent with small niches that serve as pleasant resting places for adults and hiding spots for children. About two-thirds of the way up, visitors encounter a glass-bottomed viewing platform suspended above the hollow core—a popular yet slightly nerve-racking photo opportunity that reveals the tower's architectural ingenuity.

The Library Hall: From Scholarship to Contemporary Culture

Halfway up the spiral ramp lies the Library Hall, a bright and beautiful 800-square-metre space that once housed the entire University of Copenhagen book collection—over 10,000 volumes—until 1861. The hall was restored in 1987 and reopened as a dynamic exhibition and event venue, transforming a space steeped in academic tradition into a contemporary cultural hub. Today, it hosts rotating exhibitions spanning art, science, and history, alongside concerts, lectures, talks, and activities for both children and adults. The Library Hall also features the Round Tower's shop and café, where visitors can enjoy refreshments and purchase books, posters, and other curated items. Throughout 2026, the tower will present four special exhibitions exploring the theme of light, alongside a rich programme of music and cultural events.

The Observatory: Stargazing Across Centuries

At the summit, the active observatory continues the tower's original astronomical mission. During the winter season from October to March, the observatory is manned by professional astronomers on Tuesday and Wednesday evenings from 18:00 to 21:00, offering visitors the opportunity to observe planets and celestial phenomena through the tower's large refractor telescope. On select summer Sundays, the Sun and sunspots can be observed through a special protective filter. The open-air viewing platform at the top provides one of Copenhagen's finest panoramic vistas, stretching from the spires of Copenhagen Cathedral and St. Nicolas Church to Rosenborg Palace, the Marble Church, and on clear days, across the Øresund strait to Sweden. This 360-degree perspective captures the essence of Copenhagen's historic cityscape and remains a defining experience for the tower's visitors.

Restoration and Future Preservation

In 2026, the nearly 100-year-old observatory building undergoes comprehensive restoration to protect this important piece of cultural heritage. The copper dome, worn by nearly a century of exposure, will be replaced, and the observatory's interior will be refurbished with a renewed floor and a restored refractor telescope. The Round Tower will close for most of January 2026, with additional partial closure days during the initial and final stages of work. The Public Observatory is expected to reopen in autumn 2026. During the restoration period, visitors will occasionally be able to follow the preservation process from street level, offering a rare glimpse into the craftsmanship and heritage conservation that sustains this historic landmark.

Visitor Access and Practical Considerations

The tower welcomes approximately 650,000 visitors annually and operates with a maximum capacity managed by staff to ensure visitor safety and experience quality. During peak hours, queuing may occur, though waits typically do not exceed 20 minutes. Traffic to and from the viewing platform is regulated by a traffic light system. The only route to the summit is via the spiral ramp followed by two sets of stairs—a wide wooden staircase and a smaller winding stone staircase—making the tower challenging for wheelchair users, though exhibitions in the Library Hall remain accessible. Children under 11 must be accompanied by an adult. Guide and service dogs are permitted, but other pets are not allowed. Visitors may bring their own food and beverages but cannot consume them in the Library Hall or café.