Megalithic Barrow

As you know, such things were littered around Britain and Europe during the Dark Ages.  I think it would make a great side show for a Skirmish game, as a sorcerer's hideout or perhaps a lair for the likes of Grendel.  This one is a limited run production, but provides inspiration for a scratch build.
http://www.wargamescenics.com/barrow.html

 These pics of the West Kenneth Long Barrow near Avebury are also pretty cool.