For a panoramic view of the city of Copenhagen, climb the spiral ramp (no steps) leading up to the top of this tower, which was built in 1642. The spiral walk to the top is unique in European architecture, measuring 268m (880 ft.) and winding itself seven times around the hollow core of the tower, forming the only link between the individual parts of the building complex. Obviously not wanting to walk, Peter the Great, in Denmark on a state visit, galloped up the ramp on horseback, preceded by his carriage-drawn czarina. Rundetårn is also the oldest functioning observatory in Europe, in use until 1861 by the University of Copenhagen. Now anyone can observe the night sky through the astronomical telescope.