Nidarosdomen, Trondheim

The Nidaros Cathedral is the northernmost medieval cathedral in the world. It is built over the burial site of Saint Olav, or more correctly: near by the burial site. He was the king of Norway in the 11th century and then became the patron saint of the nation. 
The cathedral was built from 1070 to 1328. It was taken from the Roman Catholics by the Lutheran Church in 1537.  

It's not allowed to take photos inside, so that's a bit unusual. Gustav Vigeland has contributed with statues inside.