This photograph, taken on 7/10/1936, shows the opened kistvaen at Ingra Tor.
It is thought that kistvaens (or cists) were interment pits. They were usually built with the end stone slabs holding the the side stones apart, and with another stone slab as a cover, but there are a great deal of variations in kistvaen construction so it is not possible to be precise.
A mound of earth, or barrow, would have covered the kistvaen. Sadly all the Dartmoor kistvaens have been opened and plundered by earlier generations, so it is impossible now for archaeologists to be sure how kistvaens were used.