When we reached the spot they had turned, we could see that a carved capstone had been rolled into place behind them.
And I, the son and grandson of Indiana architects, seize this opportunity to suggest a feature which I hope will be included in the completed structure, words to be chiseled into the capstone over the main entrance.
As with other portal dolmens, access was through the gap between the side walls and the capstone .
The largest block recorded is the capstone of the tomb at Browneshill, County Carlow, Ireland, estimated to weigh 100 tonnes.
Imagine an ancient burial site, which has the biggest capstone in Europe yet no one is able to get to it.
It is easily as large as the Great Pyramid at Giza, but it is white with a golden capstone .
Portal tombs are so called from the two large upright stones forming the entrance to the burial chamber; a capstone is set over these and slopes backwards to rest on backstones.
This in turn leads to the much larger trapezoidal burial chamber at a slightly higher level, which has survived with its capstone intact.
The capstone of the third grave had survived, however, and inside lay the fragile remains of a child aged about 9-12.
A capstone is the uppermost stone of a structure in architecture.