Photisterion

(φωτιστήριον), a place of illumination, being a term frequently used in the ancient Christian Church to denote the baptistery, or the place of baptism, that ordinance being supposed to be attended with a divine illumination of the soul. SEE PHOS, This name might also be used for another reason, namely, because baptisteries were the places in which instruction was communicated previous to baptism, the catechumens being there taught the creed and instructed in the first rudiments of the Christian faith.