Bolnisi Sioni is one of the oldest and largest of Georgian Christian religious buildings — a three-nave basilica with a projecting semicircular apse, an open arched gallery running along the whole north facade, a second small arched gallery, and a baptistery on the south side. It is built of well-dressed greenish blocks. Brick predominates in the fabric of the west wall — the result of a late restoration. The naves are divided by five pairs of cruciform piers. All three naves are covered by a single gabled roof; though the central nave is taller and wider than the others, it is not expressed externally. The central nave was covered with a full vault, the side naves with half-vaults