The castle of Gresti or Pietratagliata is located near the village of Aidone. Its current condition is that of ruin even if well legible in the forms that are composed mainly of a mighty tower full and a series of rooms ingrottate. The first historical news documented dating back to the 14th century. The castle stands on a high rocky ridge of sandstone. The central part, the spur higher, has been used by man for its strategic position as a control station and defense. In fact the castle constitutes an outpost or a fortress of sighting for the control of a vast territory, connoted by important streets of communications which from the eastern coast is addentravano toward the center of Sicily dominated by settlements which Morgantina, Enna, Agira.
The structure extends over four levels: on the first level, which is also the oldest to be found in the rural houses and a large cave which opens with a loggia south and with a window and loggia and north. At the second level from which also begins the tower full and part the scale dug in the rock, there are two local: an input and a room with window delimited by benches in masonry. At the third level, the second floor where you find the environments 'noble' representation, there are four rooms dug in the rock and other in masonry. The fourth level is present an environment with entrance portal which would suggest a chapel and a cistern to collect rainwater. A mention deserves the high tower full, firmly anchored to the rock, visible at large distances. Has walls from compact surfaces, underlined by sharp built in blocks of stone perfectly squared; access to the terrace of the tower was allowed by a beautiful spiral staircase, with steps of basalt, placed in the corner of the south-east.
For the structure and for some particular aspects, the castle may not have had the function of an aristocratic residence, but was certainly a fortress of sighting within the valley of Gornalunga that, from the earliest times, has made a connection between the Ionic coast and the interior. The presence of numerous castles like (some today recognizable only by the toponymy) suggests plausible to assume that the castle had inserted inside a network of optical signals, defined anciently fani or fires, which allowed to rapidly transmit a signal even at a great distance.
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.