St. Peter's Church have been probably built in two phases during the 12th century.The eastern part with chancel, transept and central tower were erected first during the late 1100's, while the nave and the present west tower were added later.
According the tradition the church was used as a bishop’s cathedral until 1130 when the bishop's seat was moved to Gamla Uppsala. The another legend believes the church has been a royal church. After a fire in the 1600s, the church has stood as a ruin.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.