Pentre Ifan contains and gives its name to the largest and best preserved neolithic dolmen in Wales. As it now stands, the Pentre Ifan Dolmen is a collection of seven principal stones. The largest is the huge capstone, 5 m long, 2.4 m wide and 0.9 m thick. It is estimated to weigh 16 tonnes and rests on the tips of three other stones, some 2.5 m off the ground. There are six upright stones, three of which support the capstone. Of the remaining three, two portal stones form an entrance and the third, at an angle, appears to block the doorway.
The dolmen dates from around 3500 BC, and has traditionally been identified as a communal burial. Under this theory the existing stones formed the portal and main chamber of the tomb, which would originally have been covered by a large mound of stones about 30 m long and 17 m wide. Some of the kerbstones, marking the edge of the mound, have been identified during excavations. The stone chamber was at the southern end of the long mound, which stretched off to the north. Very little of the material that formed the mound remains. Some of the stones have been scattered, but at least seven are in their original position. An elaborate entrance façade surrounding the portal, which may have been a later addition, was built with carefully constructed dry stone walling. Individual burials are thought to have been made within the stone chamber, which would be re-used many times. No traces of bones were found in the tomb, raising the possibility that they were subsequently transferred elsewhere.
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.