The church of Hosios Loukas, "Katholikon", was built in the first half of 11th century. Its architectural type is that of domed octagon with the main feature a huge dome & the main area unified & unbroken. The mosaic decoration is dominated by figures of military, of church fathers & of saints monks. The refectory has been used since 1993 as a sculpture museum, in which are exposed excellent marble parts from the monastery’s buildings. The relic of Hosios Loukas is in the lower crypt to the right of the katholikon.