Lateran Baptistery

This octagonal baptistery beside the Lateran basilica is the oldest such building in the Christian world and served as the model for baptisteries across Europe. Founded under Constantine in the fourth century and remodelled a century later, it centres on a large green porphyry font ringed by ancient columns supporting an upper order. Side chapels preserve fifth-century mosaics glittering with vines and birds against a deep blue ground. Its eight-sided plan became the form long associated with baptism.