Château d'Entrechaux stands on a rocky peak above the village and is undergoing restoration. From the site, there is a good view of the village and of the surrounding area, extending to the castles at Crestet and Beaumont-du-Ventoux. Entrechaux, the Château de Crestet and the Château de Beaumont-du-Ventoux formed an effective lookout network.
Mainly dating from the 10th or 11th centuries, the Château d'Entrechaux is actually two castles. Begun around 900, the Petit Château (Little Castle), with its fortified chapel dedicated to St Quenin and a cistern dug into the rock, was built by the Bishops of Vaison. During a long period of dispute with the Counts of Toulouse, this castle was shared with the village lord. The latter constructed the Grand Château (Big Castle), below the first, with a square keep more than 20 metres high, a chapel dedicated to St Laurent and several other buildings, surrounded by ramparts. A gatehouse with a bretèche served both castles. The joint ownership lasted for about 450 years from c.1230.
A band of outlaws pillaged and began the destruction of the castle on 9 September 1792. The sale of stones by the municipality and vandalism by inhabitants led to its ruin. The castle was treated as a quarry.
The castle is private property. Visits are possible during the summer.
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.