Jotnar Shrines are large wooden boxes that contain a story when you open both of the doors. There are 11 of them hidden in the game, although most are not hidden very well. You should come across most of these as you progress through the story. Finding them all will unlock a Playstation trophy called “The Truth”.
If you have missed any of these as you went through the story the video guide below will show you the location of every Jotnar shrine in God of War. Since a lot of these are found in areas tied to the story, you will need to make your way through the story before you are able to collect all of these.