The Round Tower
Hovedstaden
The Round Tower, or Rundetårn, is a 41.55-meter tall historic tower located in central Copenhagen on Købmagergade. Built between 1637 and 1642 under King Christian IV, it was designed as part of a complex including Trinitatis Church and served multiple functions: a university church, an astronomical observatory, and an access route to the university library. The tower is renowned for its distinctive wide spiral ramp that ascends nearly to the observation platform, originally designed to allow horses and carriages to transport heavy books and instruments. The observatory at the top is the oldest functioning observatory building in Europe, historically used by notable astronomers such as Ole Rømer. Today, it operates as a public observatory and cultural venue, hosting exhibitions, talks, and events related to astronomy and light. The tower features a wrought iron railing from 1643 and houses Ole Rømer’s planetarium machine, illustrating planetary positions based on historical and modern models. Visitors can enjoy panoramic views of Copenhagen from the platform and explore the tower’s rich scientific and architectural heritage.
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Tip: For the best experience, visit The Round Tower during clear days to enjoy unobstructed panoramic views of Copenhagen. Consider purchasing tickets in advance to avoid queues, especially during special exhibitions or events. The tower offers discounts for students and seniors. Guided tours provide deeper insights into the tower’s history and astronomy. Note that the tower is accessible via the spiral ramp, which is easier to navigate than stairs but may still be challenging for those with mobility issues.
Interesting facts
- •The Round Tower is the oldest functioning observatory building in Europe.
- •Its spiral ramp was designed wide enough for a horse and carriage to ascend to the top.
- •Tsar Peter the Great of Russia famously rode a horse up the spiral ramp during his 1716 visit.
- •The wrought iron railing around the observation platform dates back to 1643 and was crafted by royal blacksmith Caspar Fincke.
- •Ole Rømer’s planetarium machine, originally installed in 1697, shows the positions of the six inner planets and the sun according to both the Tychonic and Copernican models.
History
Construction of The Round Tower began in 1637 under King Christian IV and was completed in 1642 as part of the Trinitatis complex, which also included a church and university library.
The tower was built primarily as an astronomical observatory and access route to the library, featuring a unique spiral ramp instead of stairs.
Over the centuries, the tower’s function evolved; the library and observatory moved to newer buildings in 1861, and the church became a parish church.
The observatory was restored in 1929 to serve as a public observatory, preserving its scientific heritage.
The tower has undergone various restorations, including upcoming work on the observatory building to maintain its cultural significance.
Place Guide
Spiral Ramp1637-1642
A unique feature of The Round Tower, this broad spiral ramp ascends nearly to the observation platform, originally designed to allow horses and carriages to transport books and astronomical instruments to the top.
Observation Platform1643
Located at 34.8 meters above street level, this platform offers panoramic views over Copenhagen and is surrounded by a wrought iron railing from 1643 crafted by Caspar Fincke.
Astronomical Observatory1642 (original), 1929 (current observatory building)
The oldest functioning observatory building in Europe, historically used by astronomers such as Ole Rømer and Horrebow. It houses a refracting telescope made by G. & S. Merz in Munich with Danish mechanical parts, offering magnifications from 80 to 450 times.
Ole Rømer’s Planetarium Machine1697 (original), early 19th century (current placement)
A mechanical device mounted above the spiral ramp’s top showing the positions of the sun and the six inner planets according to historical and modern astronomical models. The current machine dates from the early 19th century with a clockwork mechanism added in the 20th century.
Contact
Phone: 33 73 03 73