Located today on one of the city center's busy shopping streets, it's easy to escape the crowds and walk up the wide spiral path to the top of the tower. In fact, it's like stepping back in time as you walk up the wide spiral path that, if you believe the stories, a Russian Tsar once rode up on a horse.

King Christian IV built the tower in the early 17th century at a time when Denmark was famous for its astronomical achievements thanks to the astronomer Tycho Brahe. After Brahe's death in 1601, the King built the tower as a way to continue Brahe's research.

Today, the observatory is still used by amateur astronomers and many visitors and is the oldest functioning observatory in Europe. It's right at the top of the tower, accessed via a spiral walk. The observatory is encircled by an outdoor platform offering magnificent views of the old part of Copenhagen.

Exhibitions in the Round Tower

The observatory isn't the only thing you can visit in the round tower. There's also a grand library hall, which once housed the entire book collection of the university. Author Hans Christian Andersen used to visit the library and found inspiration for his work here. It's no longer a library; located partway up the spiral walkway, it's now an exhibition space hosting displays of art, culture, history, and science.

Don't look down!

The whole tower is built with a hollow core - which a 12-year-old choir boy discovered to his dismay in 1880, when he fell down 25 metres while playing a game of hide and seek. Today you can look down the hole – in a much safer way – by standing on a glass floor 25 metres above the ground. The glass is more than 50 mm thick and can carry up to 900 kg per square meter. And don't worry – the choir boy was rescued!

Source : https://www.visitcopenhagen.com/copenhagen/planning/round-tower-gdk410741