The entrance is through a transverse barrel vault gopuram. It has a pointed granite roof, with a ceiling shaped like a barrel vault. Many had a "barrel vault" roofline. The transept is roofed by a barrel vault. Originally steps led down to the ambulatory, which was covered by a barrel vault. It consists of a round portico with a barrel vault supported by pillars. The edifice has a nave and two aisles with barrel vault. The ground floor has a height of 7 m and a pointed barrel vault. The narthex has three bays, whose central bay is covered by a barrel vault. Its roof was a long barrel vault with steel supports. The Main Concourse's ceiling is an elliptical barrel vault. Use of the barrel vault replaced the Hellenic use of columns to support roofs. The hall has a barrel vault roof. Colossal piers superimposed over these two tiers support the ribs of the barrel vault. The choir is roofed by a fine wooden barrel vault dating from the 14th century.