Trinitatis Church is located in central Copenhagen, Denmark. It is part of the 17th century Trinitatis Complex, which includes the Rundetårn astronomical observatory tower and the Copenhagen University Library, in addition to the church. Built in the time of Christian IV, the church initially served the students of Copenhagen University. The interior was seriously damaged in the fire of 1728 but was rebuilt in 1731. The Rundetaarn, or Rundetårn (Round Tower in English), is a 17th-century tower located in central Copenhagen, Denmark. One of the many architectural projects of Christian IV, it was built as an astronomical observatory. It is most noted for its equestrian staircase, a 7.5-turn helical corridor leading to the top, and for the expansive views it affords over Copenhagen.