Dun Ara was a stronghold of the MacKinnon clan who held the land here from 1354 onwards. The castle was still in use until the 17th century when it was abandoned. The castle was probably built on the site of a previous Dun or fort. The castle had a surrounding wall protecting a central keep or building on the main outcrop of rock. The location was valuable as it protected a harbour of boat landing as well.
The castle was fortified by enclosing the entire rock summit with a curtain-wall of stone and lime, which varies from about 1.3 m to 1.8 m in thickness. It is best preserved on the north-east side, where it rises to a maximum height of 1.8 m, but little remains on the south-west and south-east sides. The masonry was built with coarse, lime mortar, much of it has washed out of the facework giving it the appearance of dry-stone walling. It is possible that in places the lower courses of masonry pre-date the medieval castle and belong to an earlier fort that occupied the same site. The entrance is on the south-east side.
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.