I typically use these stone circles for bases and portal hubs. Things to note:

a. The stones themselves are invulnerable to damage. Earth walls can be erected in the gaps between the stones to keep ground-based enemies out.

b. A campfire or workbench placed in the center of the stone circle will keep enemies from spawning within that circle.

At some point in finishing the game, Iron Gate Studio may employ these stone circles for some purpose incompatible with viking houses and other structures. Until then, I use them whenever circumstances permit.