From the English Wikipedia page [1] - there is more information on the Norwegian Wikipedia page [2].
The Isdal woman (Norwegian: Isdalskvinnen) is the subject of unsolved case involving an unidentified woman found dead at Isdalen Valley in Bergen, Norway on 29 November 1970. Considered one of Norway's most profound mysteries, the case has been the subject of intense speculation over the years regarding the identity of the victim, the events leading up to her death and the cause of death. Public interest in the case remains significant.
The woman was found in a part of Isdalen popularly known as "Death Valley", which lies in the direction towards Mount Ulriken. Next to the scene police found a burned-out passport. The autopsy showed that the woman had suffered blunt force trauma to the neck and had taken several sleeping pills before she died. The official police report concluded suicide, but this conclusion is highly controversial.
Police eventually found out that the woman had travelled around Norway and Europe with nine different identities: Jenevive Lancia, Claudia Tjelt, Vera Schlosseneck, Claudia Nielsen, Alexia Zarna-Merchez, Vera Jarle, Finella Lorck and Elizabeth Leen Hoywfer. All of these identities were false. According to witness sightings the woman used various wigs, and in the trunk there were found several cryptic diary entries. The codes were later deciphered by police who concluded that they were coded dates and places the woman had previously visited.
There are various other websites and pages - eg [3], and with a podcast at [https://www.theverge.com/2018/7/1/17317030/bbc-nrk-death-in-ice-valley-podcast-isdal-woman-true-crime.