Frozen fortress was made to give teams a really good map for working together on.
The map takes a bit of inspiration from medieval castles, with "towers" in the corners, and a thin "catwalk" between the teammates.
Two people working together can make a very hard to reach fortress out of their side of the map.
There isn't much space to build on at the original base - which means that the two players will have to expand on to the tundra in the center of the map. Apart from the standard supply depot, there is a storage area, with some smaller supply packages, and a UN container.
There are quite a few ressources for each team, located between the players on each team. I have seen a few teams starting a fight over shared ressources, so - don't! : )