Rundetårn

Rundetårn stands in Copenhagen as a Dutch Baroque tower within the Trinitatis Church complex. Built between 1637 and 1642, it rises about 35 metres above the city. Its upper platform frames views of Copenhagen’s towers and historic buildings. A wrought iron lattice surrounds the platform, carrying Christian IV’s monogram and the letters RFP.

Hans Steenwinkel the Younger designed the project for Christian IV, while Leonhard Blasius completed it in 1643. The interior replaces stairs with a 209-metre spiral ramp winding seven and a half times around a hollow core. That route carried heavy astronomical equipment upwards, including loads moved by horse or cart. Until 1861, the building combined an astronomical observatory, a university library, and a student church. Its observatory serves public outreach and amateur astronomy, with an old telescope still standing on the roof.

A seven-metre dome, added to the observing platform in 1929, measures six metres across. Deep in the hollow core, researchers once used a toilet connected to a shaft reaching the ground floor. The unusual feature shares the building with a gilded rebus on the south façade, containing four Hebrew consonants and the year 1642.