Baptistère Saint-Jean, Poitiers

The Baptistère Saint-Jean, located on Rue Jean-Jaurès in the heart of Poitiers in Nouvelle-Aquitaine, is the oldest extant Christian building in France and one of the oldest in western Europe. Construction began in the second half of the 4th century AD, reusing the foundations and materials of earlier Roman structures, and the building was substantially enlarged and decorated during the Merovingian period (6th–8th centuries). The baptistery served as the site of baptism by immersion for the bishops of Poitiers, and its octagonal piscina — the immersion pool — remains in place at the centre of the nave. The interior walls are covered with a remarkable sequence of Merovingian and Romanesque frescoes dating principally from the 11th and 12th centuries, including depictions of the Evangelists, equestrian scenes interpreted as Constantine the Great, and fragments of celestial imagery rendered in red, yellow, and black ochre. The building's exterior displays alternating courses of Roman brick and stone, characteristic of late antique construction in the region, and the apse is decorated with blind arcading. The Baptistère was classified as a historic monument in 1840, among the first buildings in France to receive this protection, and became the property of the city of Poitiers in the 19th century. A small lapidary museum occupies the nave, displaying Roman and Merovingian funerary stelae, carved capitals, and fragments of sculpture recovered from the site and the surrounding city. The building was last restored in the 1990s and is maintained by the Direction Régionale des Affaires Culturelles (DRAC). It stands within easy walking distance of Notre-Dame-la-Grande and the Cathédrale Saint-Pierre.