[Soliton]

Very typical of glacially deposited rock

[muawiyah]

At the same time it's pretty typical of European graves of 5,000 years ago, and earlier. Here's one ~ they call these "dolmen".

The deal is you roll some glacial rocks over to a small area just big enough to surround a body or two. You put in the body(s). Then, you build the earth up around the stones and drag a large glacial rock over to cover the grave.

It's presumed the whole thing was then covered over with dirt so allyou see would be a bump in the Earth.