Ascoli Piceno Baptistery, Baptistery in Ascoli Piceno, Italy

The Ascoli Piceno Baptistery is a freestanding structure with a massive square base of large travertine blocks, some reused from earlier buildings, and an octagonal tiburio topped by a square lantern and a round cupola. Its interior is an irregular octagon with sides of about 5.5 metres, measuring 9.14 by 9 metres, and niches at the corners of the square base. At the centre of the floor lies a circular baptismal pool, and on the right a 14th- or 15th-century font stands on a twisted column.

Archaeological finds from 1828 and excavations between 1870 and 1880 suggest the interior was a pagan temple of Ascoli's forum, possibly dedicated to Hercules. Giambattista Carducci dates its use as a baptistery to the 6th century, citing the octagonal plan shared with Florence's San Giovanni and Ravenna's Arian baptistery. Restorations came before the 9th century and again in the 11th-12th, when the triangular decorations and the framing of the main entrance were added; the interior was restored in 2006.

The historian Mario Sabatucci read the square base as earth with its four elements, cardinal points, seasons and ages of life, and the octagonal tiburio as the eight souls saved in Noah's ark, cited by St Peter. The round cupola stands for eternity and paradise, the square lower part for the earthly world.

The baptistery stands at the eastern end of Piazza Arringo, just north of the cathedral of Sant'Emidio, with its main door facing the square and a second entrance toward the cathedral's Porta della Musa. The interior was restored in 2006. Look for the Roman wall remains at the base of the eastern side.

The circular immersion pool at the centre of the floor, aligned beneath the cupola's oculus, was rediscovered only in 1839 and dates to the 5th–6th century. It served men and women alike, assisted respectively by deacons and deaconesses. The 14th–15th-century font on a twisted column stands to the right.