The Church of Aghios Ioannis o Prodromos is estimated to have been built between the middle of the 5th and the middle of the 6th century AD. It is the Baptistry of an early Christian basilica and was excavated by the Italian archaeologist Morricone who, by judging by the dimensions of the Baptistry, came to the conclusion that the Basilica must have been the biggest of Kos and one of the biggest in the Eastern Christian world. It is considered the best conserved baptistry in Greece, form the early Christian period. The foundations of the Basilica lie under the graves of the modern cemetery.
The baptistry is now the Church of Aghios Ioannis o Prodromos, also called Epta Vimata (Seven Altars) because of its architectural characteristic (it is composed of seven conch shaped parts). It is dedicated to St. John the Baptist and is used as a cemetery church, situated in the Southern part of the town of Kos. The church is bipartite, its altar table is dedicated to John the Baptist and the adjacent Chapel, to its left, to Saint Haralambos. The ossuary of the city’s cemetery, the Sanctuary of Saint Lazaros, lies to the SW of the cemetery. The baptistry is quite impressive and well worth the detour.
It is square-shaped externally while the roofing forms an octagon. Inside, it is round with four niches at the corners and one in the middle of the eastern side. Its walls show a total of 7 niches, which, from the entrance to the West, resemble holy altars or sanctuaries, thus giving the name to the Baptistry (Epta Vimata or Seven Altars). The interior colonnade was made of 8 marble columns with Ionic capitals and architraves, interconnected by semicircular arches. Three of these columns remain to this day supporting the narthex, whilst the others were used to build the Lozia Mosque. A hemispherical dome of 6.5 m in diameter covers the entire building. Recent restorations have revealed murals dating back to the 12th-13th century but also the 16th century, depicting scenes from the life of Saint John the Baptist, that were vandalised during the Ottoman period. Large part of the materials used to build the Baptistry have been taken from ancient buildings of earlier periods some of which you will not fail to notice. Some archaeologists even believe that the baptistry was built on the ruins of an ancient temple, perhaps of the Pythian Apollo. Foundations of white vaulted corridors that encircled the baptistry were also found.
Furthermore, traces from the mosaics of the narthexes of the basilica were uncovered during the erection of the Chapel of the Catholic Cemetery (Cappella di San Croce), north of the baptistry. To the west of the Baptistry, excavations under today’s Anapafseos Street revealed the wide and long narthex that wounded up at its southern end in a vaulted chapel. The floor mosaic of the narthex, with doves and scarabs, was transported to the Castle of Rhodes. At a distance of 20m to the south from the baptistry, mosaic floors were discovered in 1978 covering a large area, attesting the existence of a vast early Christian complex.