It's where they got the stone for Stonehenge
I reckon the druids were doing a sacrifice one day when a bloke knocked of the temple door and said "We've been working in this area building a mausoleum and Chalkie's only gone and over-ordered the sacred stone and we don't want to have to float it all the way back to the warehouse. We could knock you up a nice little henge for cost. What do you say?"