Rundetårn, the Round Tower

Here is one of the great whims of Christian IV, the king who filled Copenhagen with towers. Rundetårn was built between 1637 and 1642 as an astronomical observatory, part of a complex designed for the University: Trinity Church, a library and the tower itself.

1A staircase with no steps

The most surprising part is inside: there are no stairs. A spiral ramp about 210 metres long winds seven and a half times to the top, almost 35 metres above the street. It was designed so that horses and carriages could haul instruments and books up.

The design is attributed to Hans van Steenwinckel the Younger, who died in 1639, before it was finished. The library hall above the church held the University’s first library, which was lost in the fire of 1728.

It is said that in 1716 Tsar Peter the Great rode up the ramp on horseback, with the Tsarina following in a carriage.

2A royal rebus

Look at the façade: the Latin inscription mixes words and symbols. The Hebrew letters of God’s name, a sword, a heart and the king’s monogram read as a prayer: ‘Lord, direct the right doctrine and justice into the heart of the crowned King Christian IV’. In 1861 the astronomers moved to a more modern observatory, but the tower still works as a public observatory in winter.

3What to look out for

• The golden rebus on the façade, with its heart and crown.
• The observatory dome at the top.
• Trinity Church, joined to the tower.