The royal mausoleum is a royal burial chapel at Akershus Castle in Oslo. The crypt is the long basement under Akershus Slottskapell; it acts as a front room for the mausoleum. It is built as a protrusion from the crypt into the walled patio garden (murinngjerdede terrassehagen) called Jomfruhagen between the castle and Jomfrutårnet on the right. The drawings for the chapel's design and location are dated April 1939. Work began in the winter of 1939/40 but stopped due to World War II.



The royal mausoleum was consecrated on December 16, 1949, it was first used for Queen Maud. She and King Haakon VII rest in a white marble sarcophagus, while Crown Princess Märtha and King Olav V's sarcophagus are in dark green, patinated bronze. The public has access, but the mausoleum itself is closed off with a wrought-iron gate in black and with gilded ornaments. There are six steps from the burial chapel up to the crypt.



In a niche in the crypt wall outside the Royal Mausoleum, the remains (skulls) of King Håkon V Magnusson and his queen, Eufemia, are mortared (innmurt). Their remains were found in a walled grave in the middle of the choir of Mariakirken (the royal burial church of the Middle Ages) during the excavations in 1858. They were then kept at the Anatomical Institute until the "burial" in 1982. Their identities have been confirmed by newer methods.



The last mentioned is Sigurd I Magnusson or Sigurd Jorsalfarer (The Crusader). Originally, he was buried in St. Hallvard's Church in Oslo in 1130. In 1665, the skull was found inside the wall in the ruins of the church, or rather what they thought was Sigurd's skull. To make a long story short, the skull was "buried" in a niche in the crypt wall in 1957; there was also set up a headstone with the king's name on it.



In 2014, however, it was determined that it was not Sigurd Jorsalfarer's skull that was buried; it probably belongs to an unknown, Danish nobleman from the 16th century. When this became publicly known, it was said that the skull should be returned to Copenhagen, the grave and the headstone to be destroyed. But until July 2019 this has not happened, instead an information poster has been set up which says that this is probably not Sigurd I Magnusson's remains.