St. Olav's Cathedral is the cathedral of the Roman Catholic Diocese of Oslo. At the time of construction, this church, being built at Hammersborg, near the graveyard of Our Saviour, was located in the countryside outside the then city of Oslo. The work was funded by private donations and fundraising abroad, the most generous individual donor being Queen Josephine, who was a Catholic herself.
The first mass of the church was celebrated on August 24th, 1856, but as there was no Roman Catholic bishop in the country, the church was not consecrated until August 8th, 1896. When the Roman Catholic Diocese of Oslo was established in 1953, St. Olav's was chosen as the episcopal seat and was elevated to the rank of cathedral. It is the second Catholic cathedral in Oslo. The St. Olav's Cathedral was visited by Pope John Paul II when he visited the Scandinavian countries in 1989.
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.