Outside the Monolithos village is the medieval castle, built on top of a 100m rock. It was built in 1480 by the Knights of Saint John to protect the island from attacks. In fact, this castle was never conquered. The Castle of Monolithos is widely ruined today but it offers great views of the sea and the two islets opposite to it. Inside the castle, there is a small working chapel dedicated to Agios Panteleimon (Saint Pantaleon).
Access to the castle is by a staircase cut into the rock. The steps, whilst not particularly steep, are quite slippery simply due to the numbers of visitors wearing them away. On the climb up to the top, you are likely to see hundreds, if not thousands, of small piles of rocks from 3–10 in number. These piles are left there by the visitors as a form of a memento.
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.