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 Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.