The 17th century tower and observatory Rundetaarn, or the round tower, is the oldest functioning observatory in Europe.
When Christian IV built the tower, Denmark was quite famous for its astronomical achievements thanks to the astronomer Tycho Brahe. When he died in 1601, the King wished to continue Brahe's research, and thus the round tower came into being.
It has been a while since the scientists left, but the observatory is still used by amateur astronomers and the many visitors. The observatory is encircled by an outdoor platform from which you have a magnificent view of the old part of Copenhagen.
To get there you need to walk up the spiral walk, which is 268,5 meters long at the outer wall and only 85,5 meters long close to the core of the building. This means that you walk around 209 meters to get to top even though the tower is only 36 meters tall.
The tower from inside
This walk also leads to the library hall, which once housed the entire book collection of the university. The famous Danish writer H.C. Andersen used to visit the library and he found inspiration for his work here. Today the hall serves as the framework for exhibitions of art, culture, history and science.
Floating glass floor
As a new attraction you can now see the tower's core by standing on a glass floor, hovering 25 metres above the ground. The glass is more than 50 mm thick and can carry up to 900 kg per square meter.