The Long Barrows

The neolithic "long barrows" found in Britain are megalithic earthworks, generally assumed to be tombs. Though remains have been excavated in many of them, the haphazard placement of those remains doesn't indicate any kind of ritualized burial: the intent of these structures is still a mystery. Their design, especially at the entrance, does suggest a birth passage. The photo above is of an entrance to the Belas Knap Long Barrow, built some 2000 years BCE.