The monastery is the jewel of Sant Cugat. This monastic compound was the most important in the county of Barcelona in the medieval period. Today it consists of the church and a cloister, which houses the central part of the Museum of Sant Cugat and which offers a free guided visit on the first Sunday of the month at 12 noon. The chapter house and the old monastic rooms are placed around the cloister, and the abbatial palace to the west. Of the compound, which was totally fortified, a significant part of the walls and towers remains. They were built in the 14th and 16th centuries. The Romanesque cloister (12th century) is the most outstanding feature for its structure and the decorative quality of the capitals. In the 16th century a second floor was added and the atrium was built. More than thirty metres long, the cloister is work of the artist Arnau Cadell. The layout is almost square, with semicircular arches, supported by pairs of columns. Each column is decorated with finely tooled capitals, with details varying from a representation of animals to advice on good behaviour for the monks (for example, how to help brothers to remove lice). There are 72 pairs of capitals. Another outstanding feature is the Gothic basilica. The building, 52 metres long and 23 metres wide, has three vaulted naves, supported by columns. The rose window, 8.2 metres in diameter, is very similar to those in the cathedrals of Barcelona and Tarragona. The church conserves the All Saints altarpiece (1375), by Pere Serra, one of the most brilliant testimonies to the Catalan Gothic school. The origins of the monastery go back to the 9th century, when it was decided to join the church containing the remains of Saint Cugat to neighbouring fortification. Therefore, it was built on the base of a paleo-Christian church of the 5th century, a small square area around which it is believed a community of monks already existed. However, documentary evidence only exists from the year 878. In the mid 12th century construction of a new monastery began. The existing church was enlarged and in 1350 work was undertaken to fortify the monastery. In order to improve the supply of water, an aqueduct was built in the 14th century, from which today the Can Vernet bridge is a remnant. During the War of Succession, the monastery was occupied by the troops of Archduke Carlos, causing serious damage. Later repairs were completed in 1789. In 1835 the monks left the monastery and in 1851 the Commission of Historical Monuments decided to restore it. In 1931 it was declared an Historical Artistic Monument.