A seventeenth-century observatory in Copenhagen is reached not by stairs but by a continuous helical ramp wide enough to have once accommodated horse-drawn carts.
About The Round Tower
Built 1637-1642 under Christian IV as part of a university complex, the Round Tower housed the Copenhagen University Observatory for over two centuries. Ole Rømer used its telescopes in 1676 to calculate the speed of light.
Overview The Round Tower — Rundetårn — stands in central Copenhagen as one of the city's oldest preserved structures and one of the more unusual examples of seventeenth-century scientific architecture in Europe. Built between 1637 and 1642 under Christian IV, it served as the observatory for the University of Copenhagen for over two hundred years. What makes it physically distinctive is its interior: instead of stairs, a continuous helical ramp winds 7.5 turns to the top.
“Built between 1637 and 1642 under Christian IV, it served as the observatory for the University of Copenhagen for over two hundred years.”
The Round Tower, Denmark
The Story Behind It Christian IV commissioned the tower as part of a complex that included a church and a library — an attempt to make Copenhagen a center of learning comparable to the great European university cities. The observatory at the top was used by the astronomer Ole Rømer, who in 1676 calculated the speed of light using observations made here. The ramp, rather than stairs, was designed so that horse-drawn equipment could be brought to the upper levels during construction and for subsequent use — a practical solution that became the building's defining architectural feature.
What You'll Experience The ascent is the experience. The ramp is wide and gently graded, so the climb is less demanding than it sounds, but it is long — and the continuous curve creates a spatial experience unlike any normal staircase. At the top, an observation platform offers a 360-degree view over Copenhagen's historic center. The tower occasionally hosts temporary art exhibitions in its interior gallery space, and the small observatory retains working telescopes that are opened to the public on clear winter evenings.
Getting There Rundetårn is in the Indre By neighborhood, a short walk from Strøget and the main pedestrian shopping street. It's one of the most accessible historic structures in Copenhagen.
“Getting There Rundetårn is in the Indre By neighborhood, a short walk from Strøget and the main pedestrian shopping street.”
The Experience
Climb the 7.5-turn helical ramp to a panoramic platform over Copenhagen's rooflines. Browse temporary exhibitions in the gallery space, and on clear winter evenings, use the working telescopes in the historic observatory.
Why It Matters
One of the best-preserved examples of seventeenth-century scientific architecture in Scandinavia, and the site of one of the most important astronomical observations in history.
Why Visit
The ramp alone justifies the visit — the spatial experience is genuinely unusual. The historical connection to the speed-of-light calculation adds intellectual weight to what might otherwise feel like a simple tower climb.
Insider Tips
- 1
Public telescope evenings run on Tuesdays and Wednesdays in autumn and winter — check the schedule online before visiting.
- 2
The gallery space hosts rotating exhibitions that are worth checking in on; quality varies but is generally high.
- 3
The tower is in the middle of a busy shopping district — visit early morning to avoid peak tourist traffic.
- 4
Look down through the glass floor at the top of the ramp to see the well below — it runs the full height of the tower.
