A large ritual enclosure was excavated. Findings include marked or shaped stones, ritual pits, various animal and human bones (both adult and infant), post holes and a cremation hearth. A central grave contained an urn with bones and small pots around it. There were other cremation graves, as well as an adult skeleton with no grave goods. In another pit, the bones of an infant were found.

At Maiden Castle barrow, the hacked up body of a 30 y/o man was found inside a pitch-coated woven basket. Etched on the outside are the words SATOR, AREPO, TENET, OPERA, ROTAS, each five-letter group placed one above the other in a block. The words are the same back to front, up or down. Inside the "coffin" with the dismembered body was a shield, war club and "scramasaxe." Also found in the same grave were the skeletal remains of a 2-3 y/o child and a gold talisman.

Cadbury Castle. Scroll down to section: Preliminary remarks about the pits.

To answer Vortigern's question, I guess the similarities would be that all three sites bear evidence of ritual human sacrifice, which is highly disputed in certain circles.