Ledesma still has most of the granite wall which historically has surrounded the town. A large part of what is still standing was built in times of Fernando II of Leon, in the 12th century, but in the 15th century several parts of it were rebuilt with well-carved masonry. Many stone mason marks can be seen among these stones. Out of the eight doors it once had, the only one that is still preserved is the one called Puerta de los Mártires, de San Nicolás or Caldereros (Martyrs’, San Nicolás or Boilermakers’ door). Formed by two camber arches, it is flanked on either side by two cylinder towers.
The bailey of this castle-fortress was built on the south-west end of the walled area between the 13th and 14th centuries. Set on an irregular trapezoidal plan, it has two doors: one on the north, which features the town’s coat of arms, and one on the south, flanked by two large towers.
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.