The famous Dolmen in Bagneux is probably one of the most majestic French dolmens and the largest of the 4,500 dolmens spread out on about 60 French departments.The overall length of this dolmen is over 23 meters (75 feet) and its chamber is over 18 meters (60 feet) long. As all dolmens, the 'Great Covered stone" in Bagneux, was a large chamber tomb which must have contained a great number of prehistoric skeletons during the neolithic age, i.e.from 4,000 to 2,000 B.C., that is about 5,000 years ago.
Only suppositions can be made on the way the dolmens were built.The flagstones must have been raised several times with numerous levers while pebbles were slid underneath the stone.Once it was raised to a certain level, and lying on a heap of pebbles, it was easier to pull it further. Then, the same operation started all over again.
References:The dolmens and other megaliths (pyramids, cromlechs, and others) were built for defense. Read more http://forum.ozersk.ru/topic/32337-raskritie-tain-drevnosti/
The Broch of Clickimin is a large and well preserved, though somewhat restored broch near Lerwick. Originally built on an island in Clickimin Loch (now increased in size by silting and drainage), it was approached by a stone causeway. The water-level in the loch was reduced in 1874, leaving the broch high and dry. The broch is situated within a walled enclosure and, unusually for brochs, features a large 'blockhouse' between the opening in the enclosure and the broch itself. Another unusual feature is a stone slab featuring sculptured footprints, located in the causeway which approached the site. Situated across the loch is the Clickimin Leisure Centre.