Olav Haraldson fell in the Battle of Stiklestad 29. July 1030. He had lost the battle for his kingdom and failed in christening the country - or so many believed. The king's body was smuggled by loyal farmers from Stiklestad to 'Kaupangen', the then small market-town of Trondheim and buried in a sandbank outside the town. It was important to hide the body from his enemies, who were well aware that a dead king can be as problematic as a living one. News soon spread of the king's grave and the men and women who supported King Olav sought out his resting place. Before long it was rumoured that miracles had taken place by the grave and that an unexplained light was seen shining there during the nights. Word spread that Olav was a holy man. Rumours of Olav's saintliness became so persistent that on 3. August 1031, one year after his death, the decision was taken to open his grave and examine the body. Present at the examination was Bishop Grimkjell, who had been brought to Norway by King Olav to be responsible for the missionary work, the leading men and women of the land, including Alfiva, mother of the Danish king Svein who had claimed the throne after Olav's death. According to Snorre's Olavssaga, the body was without blemish, no putrification had set in, hair and nails had continued growing and a sweet scent rose from the body. Alfiva is reported to have said that "slowly rots a body buried in sand", but there was no doubt in the minds of the Norwegian men nor in the mind of Bishop Grimkjell: Olav was a holy man. The body was placed in a shrine and brought to the St. Clement's Church, the town's first church, where it was set on the high altar. This took place on 3. August, the day now celebrated as St. Olav's Translation, or sanctifying. Olav's fame as saint spread quickly and soon pilgrims started flocking to Trondheim.

The Danish King Svein had to withdraw from Norway. Olav's son Magnus (the Good), who was fostered in Russia, was brought home and taken as King of Norway. It was Magnus who first erected a small wooden church over the site of the original grave. This church was later rebuilt in stone by his nephew Olav Kyrre (the peaceful), and this stone church was the start of the Cathedral we have today. It is no accident that the church stands where it does. The sandbank where Olav first was buried lies today directly underneath the Octogon and the High Alter of Nidaros Cathedral. Olav's death won for the country what his life had failed to achieve, Norway became a Christian country.