I used the teleport pyramid to get off the main map in Hiberheim. You can see how to do that here: https://www.youtube.com/watch?v=5lJw8NVy6nk

After beating the game I spend 2-3 hours exploring 100% of every map. The only way to do that was to get off the main map and go into the template. The first picture you see is the template of Hiberheim. If I moved just a bit more inside that you could see the main map.. There were almost no building in Hiberheim, but if you go to other areas you can see more buildings. This was the only building that I did not explore. I could not fully explore because as soon as I crossed a gully frame rate of the whole game just dropped and I could only move my character every 30 seconds.

Both pictures are of the same room just different map view. The first is the map template. The second is the actual room map. The map changes when you actually enter the room, you can see that the room is the exact same orientation as the larger map, if I shrunk the picture and put it in the hole you would see they are the same rooms.

As for a little more information about the room. Absolutely nothing is interactable in it. No triggers, no items. There are stairs and ice jutting out every where. It kinda seems like a throne room.