These structures resemble henges, which are defined as a circular earthwork with a ditch inside the earthwork. Most defensive earthworks have the raised bit inside the ditch so the defenders have higher ground while the attackers are left to scramble through the ditch and then try to climb the earthwork.
Stonehenge is a henge with standing stones inside the ditch perimeter. It's a bad example to keep using as most people will keep thinking henges are the standing stone circle because of the name of the site.
The Brits think the henges are ceremonial partly because of finds inside the henge and partly because it makes no defensive sense. Some chaps think it might be to keep the dead enclosed, i.e. the inside ditch keeps them from escaping and haunting the living.
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