ORSERA. - An Istrian municipality near Parenzo. Ursaria appears in the « Tabula Peutingeriana », where the name is assigned to an island corresponding in position to O.
A centre of agricultural and commercial activity in the Roman period (it has an excellent natural harbour), it provides an uncommon example of a domus ecclesiae, discovered in 1935 near the sea. Among its various areas, noteworthy are the Basilica (9.30 x 15.20 m.), built on a rectangular plan in the mid-4th century with the two adjoining liturgical rooms, furnished with an apse and a narthex in the mid-5th century, and a small hall, identifiable as the catechumenate, contemporary with the Basilica. The latter partly preserves its mosaic floor, composed of 91 roundels of two sizes, connected by braided bands and adorned with various symbols, including the seasons. The floor mosaic of the catechumenate consists of curvilinear quadrilaterals and has a fishpond. Inscriptions are entirely lacking. The mosaics are notable for the elegance of their geometric motifs, the impressionistic rapidity of their representations, their vivid sense of colour, and certain connections with African pavements.
Near this early Christian complex stands the church of S. Maria a Marina, with three naves (12th century), to which a Franciscan convent was attached; in the town there was a small Romanesque church, the former parish church, destroyed in 1941.