Osios Loukas Monastery is one of the finest examples of a Byzantine monument in all the country. It is located at a distance of 20 km from Arachova, near Steiri village on the west slopes of Elikonas. Its construction dates back to the 11th century, while the building of the Catholic of the Monastery is attributed to the three emperors of Byzantium: Romanos II, Vasilios Voulgaroktonos and Constantine IX the Gladiator.
The monastery consists of two churches (the church of the Virgin Mary and the Catholic), a belfry, the cells and other buildings. The entire site is dedicated to the local miraculous saint, whose name it bears. The main building -the octagonal church with dome- holds the remains of St Loukas, whose memory is celebrated on February 7.
The smallest church found to the north of the main building is dedicated to the Assumption of the Virgin Mary. In 1938 and for many subsequent years, maintenance work was carried out and restoration of the Altar and the buildings, as well as cleaning of the murals and mosaics by the Archaeological Service and Archaeological Society.