Saw a post months ago where a player said he built a base in one of these. He liked the idea of incorporating those 7 indestructible rocks in his defenses.

So one of those formations is where I built my current main base. Raised earth walls six to eight meters in height between the giant stones to form an outer perimeter. The greylings, greydwarves, trolls, skeletons, and draughr seem disinclined to climb over these walls. A viking with decent stamina can do so easily.

The base has a small footprint especially at ground level. Most of the living and working areas are on an upper level anchored to either those indestructible giant rocks or earthen columns raised for the purpose.

No room for animal pens and crop fields. I placed those on a bare hillside a couple of hundred meters away, outside of the red circle appearing during raids and events. Not very convenient when planting or harvesting or feeding boar but it keeps animals and crops safe.

Strategy during raids so far is to hop ever earthen walls at one point, lead raiders on a merry chase around the main base structure but still inside red circle. Hop back over earthen walls if things get dicey. Recover health and/or stamina. Then hop back out over earthen walls to renew the chase. Works well so far. Got killed one time when I had to answer the doorbell during a raid.

Killed Bonemass yesterday so now I will see how it fares with drakes.