The Fjordur Portal Cave entrance is not too hard to find; it is in the center of the map at 70.3 - 57.5. Inside the Portal Cave, also known as the Place of Hidden Worlds, are three terminals that take you to other worlds. There is no danger in the Portal Cave other than what lies on the other side of the portal.
Fjordur Portal Cave Coordinates
|Location of the Fjordur Portal Cave|