Margaret's Castle is a small Tower house probably built in the 15th century. Only two storeys still exist but there is evidence that it was at least three storeys high. It is vaulted above the ground floor with a rectangular tower with projecting turrets in the north west wall. The doorway between the turrets was protected by a murder-hole. A spiral stairway rises within the west turret.
Ardglass had at least six castles and remains of four of them can still be seen: Ardglass Castle, Cowd Castle, Margaret's Castle and Jordan's Castle.
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.