If anyone visits Carnac...just south of the Kercado alignments is a complete passage grave....when I visited(4 years ago) people were milling about outside..until I crawled into the actual passage(it is permissible for visitors to enter btw),then others followed suit.I was pointing out to my children that the circular one piece stone ceiling/roof appears not to be held up by anything...but the whole stone has been carved with a lintel style lip all the way round...bearing in mind this is a perfectly circular stone...there must have been some effort went into the construction of this to knock that out with just hammer stones...is it possible these stones have a high lime content which can be "softened" by an acidic liquid?..Try pouring vinegar on marble to see what I mean
Apropos of nothing..there are faint carvings inside...(which I pointed out to the others in there on that occasion...and they took photographs,one dutchman insisted on snapping me pointing at the carvings and crouching by the entrance...fame at last!)but they are so faint they couldn't have been made with the same tools which shaped the stones
The large stones we call henges aren't the bluestones from Wales though are they??Are they indigenous, glacial deposits or brought from far away??