The Montemirabile or Saint John the Baptist Chapel, otherwise the Baptistery () is the first side chapel in the left aisle in the Basilica of Santa Maria del Popolo. History The chapel is named after Giovanni Montemirabile (an italianized name for Jean de Montmirail), the bishop of Vaison and confidant of Pope Sixtus IV, who was buried here after the chapel had been built in the 1470s. This was the first of the original four identical chapels on the left side and it was dedicated to St. John the Baptist. The chapel was transformed into the baptistery of the basilica in 1561. After 1568 a Renaissance funeral monument was built for Cardinal Francesco Abbondio Castiglioni by the right side wall. The monumental Renaissance wall tomb of Cardinal Antoniotto Pallavicini was transferred to the chapel in the second quarter of the 17th century, its bulk partially hiding from view or replacing the original painted decoration of the left wall. In 1657 fragments of a demolished quattrocento monument from the choir were reassembled in the chapel in the form of two aediculae by Cardinal Flavio Chigi, the nephew of Pope Alexander VII, who was Cardinal-Priest of the basilica at the time. Sometime before 1674 a new painting was made for the main altar by Pasquale Rossi. The previous altarpiece depicted the same subject bearing an inscription: Ex piorum amicorum elemosynis, meaning "from the gifts of the pious friends". This shows that the chapel was not under the patronage of any particular family. Description Although the chapel retained its basic architectural layout, many of its features were lost during the later alterations. The side walls of the windowless, hexagonal chapel are articulated by painted Corinthian pilasters decorated with tendrils, vases, flowers, animals, sphinxes, phantastic creatures and garlands on a yellow background, resting on a fake marble pedestal. These were created by the workshop of Pinturicchio. The vault is simply painted white. The keystone bears the escutcheon of Pope Sixtus IV encircled by an egg and dart moulding. The entrance arch of the chapel is painted to look like grey marble; it is decorated with a band of acanthus leaves and an egg and dart edge. Aediculae The most valuable works of art in the chapel are the aediculae of the baptismal font and the holy oil (oleum sanctum) on either side of the main altar. They were assembled in 1657 from 15th-century marble