Hosios Loukas is a historic walled monastery situated near the town of Distomo, in Boeotia, Greece. It is one of the most important monuments of Middle Byzantine architecture and art. The monastery lies on the west slope of Mt. Helikon, below the acropolis of ancient Steirion. It is enclosed by a wall and comprises two- and three-storeyed blocks of cells, a bell-tower at the SW corner, the Refectory on the south side and the two adjoining churches, at the centre of the enclosure.
Togehter with the monasteries of Daphni and Nea Moni of Chios they form a signle world heritage site. Although geographically distant from each other, the three monasteries belong to the same typological series and share the same aesthetic characteristics. The churches are built on a cross-in-square plan with a large dome supported by squinches defining an octagonal space. In the 11th and 12th centuries they were decorated with superb marble works as well as mosaics on a gold background, all characteristic of the 'second golden age of Byzantine art'.