Before the current Avaldsnes church was constructed, there was a wooden church on the same site. That church is assumed to have been built by Olav Trygvason, and it is possible that the present stone church is built around this church originally.
The current church has been a landmark for seafarers passing through the strait of Karmsund for 750 years. King Håkon IV Håkonsson gave permission to build a church around the year 1250. It was not completed until nearly 1320, and was then the fourth largest in the country. The church was dedicated to St. Olav and received the status of 'Royal Chapel'. During the same period it became one of four 'college-churches' (it appointed a council of theological and juridical scholars). Probably there was a group of four scholars and teachers in law and theology. There could be there was an octagonal house of stone in close proximity to the quire. Chapter Houses (Kapittelhus) were common for English cathedrals. This is assumed to have been referenced by clergyman and historical writer Peder Clausen Friis in 1599. Remaining walls were visible as late as 1840, but are now completely gone.
The history of the church depicts a fine cross-section of Norway's history. Being one of the largest churches along the coast of Norway, it is certain to have been visited by many travelers on their pilgrimage to St. Olav's shrine in Trondheim.
Decay started with the Black Death in 1349–1351. This disaster was followed by 400 years of Danish supremacy. In this period, the church gradually fell into a state of ruin due to lack of repair. In the 17th century a little wooden church was built inside the stone walls. This one was used for more than 200 years.
The first restoration work began in 1830. The old steeple was demolished, the nave was rebuilt, and a small wooden steeple was erected on the top. In the 1920s the church was once again restored in a manner which was more similar to its original architecture. A new stone steeple was built and the interior renewed.
The German occupation in World War II became dramatic for the church. The Germans asserted that the high steeple was used as a landmark for allied planes, coming in over the strait of Karmsund to drop bombs in the water. German authorities demanded the steeple be demolished. Many people were engaged in the task of saving it, and they persuaded the Germans to let them camouflage the whole church with timber. This was to be done in 5 weeks, but the whole job lasted a year.The 700th anniversary of the church in 1950 was a big event for the community, with concerts and a historical outdoor play which pictured the Viking history of the place.
The stained glass windows were ordered for the anniversary. They were made by Bernhard Greve, a Norwegian painter, and present the most important events in the life of Christ : Baptism, passion, ascension and resurrection.
The pointed arches, but thick walls and no pillars, suggest an early Gothic design. The walls are composed of ordinary gray stone in thickness about 1.2–2.0 meters. The corners and frames around the doors and windows are of steatite (soapstone) from Tolgetjønn near Haugesund.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.