The Rundetaarn, or the Round Tower, is an iconic 17th-century tower located in central Copenhagen, Denmark. Built by King Christian IV as an astronomical observatory, it is one of the most emblematic structures in Denmark and a significant symbol of the scientific advancement of the age. Constructed between 1637 and 1642, the Round Tower stands tall at 34.8 meters (114 feet). Its distinctive cylindrical shape is a perfect representation of Danish architecture in the Renaissance period. The exterior is a blend of Dutch Baroque and Scandinavian Classicism, an architectural style that was quite popular during King Christian IV's reign. Its façade, made of red brick, is adorned with yellow sandstone decorations, and displays the King's monogram and various astronomical and astrological symbols. The interior of the Round Tower is as intriguing as its exterior. Perhaps the most unique feature is its equestrian staircase, a 7.5-turn helical corridor leading to the top. This spiral ramp was designed to allow a horse and carriage to carry books and instruments to the library and observatory at the top. Halfway up the tower, there is a small, beautiful, whitewashed church called the Library Hall, which was once the university library and now hosts exhibitions and concerts. The Round Tower’s main attraction is its astronomical observatory, the oldest functioning observatory in Europe. It is capped by a copper-clad observatory, offering breathtaking panoramic views of Copenhagen. The observatory is equipped with a variety of historical astronomical instruments, reflecting its rich history as the hub for astronomers. In addition to its primary functions, the Round Tower has also held a number of weather stations, and its height has been used for various scientific experiments, including a famous experiment by the physicist Ole Rømer in 1679 to measure the speed of light. With over 400 years of history and a unique blend of architecture, science, and culture, the Round Tower continues to draw thousands of visitors each year, making it a must-visit destination in the heart of Copenhagen. Whether it's for the fascinating historical facts, the stunning views, or the chance to walk up the unique spiral ramp, the Round Tower offers a unique and unforgettable experience.