Ravenna’s oldest monument was erected by Bishop Ursus around 400, alongside his long-ago destroyed basilica on the site of an ancient Roman bath—the eight sides of the octagonal structure represent the 7 days of the week as set out in Genesis plus the day of the Resurrection, when Christ gave us eternal life. Bishop Neon embellished the structure at the end of the 5th century, adding the intensely colored blue, green, and gold mosaics that carpet the dome and show John the Baptist baptizing Christ in the River Jordan, surrounded by a procession of the 12 Apostles carrying crowns as a sign of celestial glory. Many of the marble panels in the walls were taken from the Roman bathhouse—that structure, like the sunken baptistery, was at street level, which has risen more than 3m (10 ft.) over the intervening centuries.