baptistery
The building or room used for Baptism. It had a font usually in the form of a cross. After the 6th c. the baptisteries constitute distinct constructions- octagonal, circular, cruciform- detached to the church or its courtyard.

basilica
In ancient Roman architecture a large oblong type building used as hall of justice and public meeting place. The roman basilica served as a model for early Christian churches.

hypocaust, the
the main system for the heating of ancient baths. The word means literally a “furnace that burns underneath”. With this system the room’s floor was supported by small poles and the space underneath the floor was heated by the circulation of hot air, while the heat was transferred through the walls by conductors.

three-aisled basilica
An oblong type of church internally divided into three aisles: the middle and the two side aisles. The middle aisle is often lighted by an elevated clerestory. In the Early Byzantine years this type of church had huge dimensions.