The Round Tower was built as an observatory in 1642 by King Christian lV.

King Christian IV and Tycho Brahe King Frederik II's son Prince Christian - later King Christian IV (1577-1648 – ruled Denmark and Norway 1588-1648) showed a great interest for astronomy too and often visited Tycho Brahe at his Uraniborg observatory on isle of Hven. As King Christian IV did not share the same enthusiasm for Tycho Brahe’s scientific methods and his interest for alchemy as his father had - Tycho Brahe fell into disgrace with the new King, who stopped all further funding of the two observatories on Hven. After the heavy dispute with King Christian IV, Tycho Brahe left Hven in 1597 and moved later to Prague. Shortly after his death in 1601, Tycho Brahe’s observatories Uraniborg and Stjerneborg was demolished and leveled to the ground.

The Trinitatis Complex After Tycho Brahe’s Uraniborg and Stjerneborg was destroyed and the lack of an having a scientific observatory in Copenhagen for the scholars and students at Copenhagen’s University – King Christian IV, who also was known as the great architect and builder of Copenhagen, took the initiative after advice from his own astronomer Christian Longomontanus to establish a new observatory, in the Latin Quarters of the City and named it the Round Tower. The foundation stone was laid in 1637 and was the first stage of the King’s Trinitatis Complex, which had the main objective to congregate three major facilities for scholars and students at the University such as an astronomical observatory – a University Church and a University Library.

The Round Tower - Copenhagen The Kings original idea from the start was to build an observatory identically like Tycho Brahe’s Stjerneborg on the top of the Round Tower with the exact diameter like Stjerneborg’s 15 m. The Tower was completed as an observatory with a little planetarium in 1642 and has a height of almost 40 m including the obsavatory. The Round Tower is built with a 210 metre long spiral ramp, which leads to the top, and on the uppermost facade of the tower (Top photo) there is a gilded inscription like a rebus. The rebus can be interpreted in the following way: Lead God, the right teaching and justice into the heart of the crowned King Christian IV, 1642 - the year when the tower was completed. King Christian IV's draft of it, written with his own hand, is kept at the Danish Record Office. The oldest functioning observatory in Europe The Round Tower is the oldest functioning observatory in Europe. Until 1861 it was used by the University of Copenhagen - but today - anyone can observe the night sky through the fine astronomical telescope of the tower in the winter period. Legendary astronomers having used the observatory include Ole Rømer (1644-1710) and Peder Horrebow (1679-1764). As a curiosity - a little piece of Tycho Brahe’s burial cloth obtained from his final resting place in Prague is displayed in the Round Tower’s collection.

The Trinitatis church and University Library As a part of the Trinitatis Complex, the Round Tower is built together with Trinitatis church as it was the King’s idea to build a University Church especially for scholars and students at Copenhagen’s University. The foundations stone was laid by the King in 1637 and the Church was inaugurated in 1656. In 1728 the church was damaged by a fire and was rebuilt again in 1731. The loft of the Trinitatis Church was used as a library for the University until 1861. The Altarpiece and pulpit is from 1756-1767 and there is a tomb under the Choir with many prominent persons buried.

Beautiful view from the top On the top of the Round Tower there is an exquisite view 40 m over the old part of Copenhagen and visitors can see some of King Christian IV's buildings like Rosenborg Castle - Old Stock Exchange (Børsen), Naval Quarters (Nyboder) - The Town Hall - Copenhagen's Cathedral and much more.

Many Challenging rides to the top King Christian IVs historical monument and landmark - The Round Tower – has been a subject for many challenging actions with its special is 210 metre long spiral ramp that leads to the top. In 1716, the royal Empress Catherine I of Russia drove up to the top of the Tower in a horse carriage, with her husband Czar Peter The Great of Russia in front on horseback, to enjoy the beautiful view over Copenhagen. The happening created headlines in the newspaper and was the talk of the town at that time. In 1902 a German tourist visited Copenhagen in his new motorized vehicle, a German Beaufort and drove his car to the top of the tower, as first motorized vehicle ascending the tower. A tradition every year in spring is the one wheel cycle rally Unicycle) up and down the towers spiral ramp and this very special arrangement by the Royal Roundtower Unicycle Race organizers gathers many participants and spectators. The world record for this special sporting event - up and down the ramp - is 1 minute 48.7 seconds - and was set in 1989.

The Round Tower.