The church of Hosios Loukas is the oldest preserved example of the complex octagon type, on the interior of which a single, uninterrupted space was created beneath a broad dome. The product of Constantinopolitan workshops,  the   building   preserves  its  original   splendour  and high aesthetics thanks to its superb mosaics and frescoes, marble-paved floors, and walls with their marble revetments. The most probable dates of inauguration of the church are considered to be 1011 or 1022.

According to his Life, Hosios Loukas (|953) settled in the Stiris region in 946 and established a monastic community there. The activity and miracles wrought by Hosios Loukas made the monastery an important pilgrimage site to which throngs of believers flocked to be cured. Between the 10th and 12th century, the first group of structures, which had been built by Hosios Loukas himself, was redesigned and evolved into a brilliant monastic complex. A second major building period began in the 16th century when the katholika were repaired, and the surrounding wings of monks' cells as well as ancillary and storage areas were rebuilt.

(Description copied from the official UNESCO leaflet available to the public)