We have already spoken of the eucharistic celebrations of which the cubicula were the scene; and still existing baptisteries prove that the other sacrament was also administered there.
The font itself is interesting for its early form, one common in the chief baptisteries of northern Italy: like an island in the centre of the great octagonal tank is a lobed marble receptacle, in which the officiating priest stood while he immersed the catechumens.
Baptisteries belong to a period of the church when great numbers of adult catechumens were baptized, and when immersion was the rule.
After the 9th century few baptisteries were built, the most noteworthy of later date being those at Pisa, Florence, Padua, Lucca and Parma.
Some of the older baptisteries were very large, so large that we hear of councils and synods being held in them.