Bishop Arnaldur (1124-52) returned to Norway in 1150 from Gardar, Greenland and was appointed first Bishop of Hamar. He began to build the cathedral, which was completed about the time of Bishop Paul (1232-52). Bishop Thorfinn of Hamar (1278-82) was exiled and died at Ter Doest in Flanders. Thorfinn and many other bishops of the area disagreed with the sitting King Eric II of Norway regarding a number of issues, including episcopal elections. Bishop Jörund (1285-86) was transferred to Trondhjem.
In the aftermath of the Reformation in Norway, the structure was renamed Hamarhus fortress and made into the residence of the sheriff. The cathedral was still used but fell into disrepair culminating with the Swedish army’s siege and attempted demolition in 1567, during the Northern Seven Years' War. Swedish forces had launched attacks into Eastern Norway, capturing Hamar and continued towards Oslo. The Swedes later retreated, torching Hamar on their way, destroying Hamar Cathedral and Hamarhus.
Today the ruins of Hamar Cathedral form a part of the Hedmark museum (Hedmarksmuseet). The ruins of what remain of the Hamar cathedral, were originally built in Romanesque architecture and later converted to Gothic architecture. The distinctive arches in the cathedral ruins are covered in one of the most ambitious construction projects of its kind undertaken by the Norwegian government.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.