The church is a sacred place where everything refers to the divine Mystery. Already at the main door, itself a symbol of Christ (“I am the door,” John 10:9), are the emblems of the Lord’s Passion and of the Holy Nail. In the same way, entering the church, we find ourselves at the foot of a cross formed by the nave and the transept cutting across it.
The central nave is the space where the community of faithful assemble to take part in the liturgy, while the two side aisles, flanked by chapels, are areas of transit towards the focus of the celebration, the high altar.
The altar, positioned at the intersection of the cross, is the place where the sacrament of the Holy Eucharist is celebrated in memory of Christ’s sacrifice, during which the Last Supper happens again, and with it the Passion, Death, Resurrection, and Ascension of Christ are relived. Above the altar is a marvelous bronze crucifix cast by Pietro Tacca on a model by Giambologna. On the left is the cathedra, the bishop’s throne, while in the apse is the choir where the clergy sat during celebrations, both of these carved by the master craftsman Silvestro Ceramelli in 1628 .
The transept terminates at either end in a chapel: on the left is the Chapel of the Holy Sacrament, where the tabernacle holding the consecrated Host, the Real Presence of Christ, stands on the altar made of semiprecious stones by Florentine craftsmen; on the right is the Chapel of the Holy Nail, which holds this precious relic, a testament of Christ’s Passion.
The baptismal font by the Florentine Domenico Rosselli, visible from the altar, was originally located in a chapel next to the Co-cathedral used as a baptistery, thus outside the space of the church proper, since baptism marks the person’s entrance into the community of believers.
In the nave, in 1465 Rosselli made the pulpit, supported by columns, used for preaching. The artist reutilized fourteenth-century reliefs of The Virgin and Child, Saint John the Baptist, and Saint Peter, and added two new panels for the sides showing Saint Albert and Blessed Pietro Gargalini. Above, an inscription urges the faithful to place greater consideration on the righteousness of the preacher than on his oratorical ability. The roof over the pulpit bears the symbol of the Holy Spirit who must inspire the speaker’s words.