The church, dating from the late 11th century, was built on the initiative of Archbishop Daiberto and completed thanks to the generosity of Countess Matilda of Tuscany. The Church is dedicated to the martyr Saint Ermolao, the protector of Calci and the Val Graziosa (the area around Calci at the foot of the Pisan Mount), who is traditionally celebrated with a feast at the beginning of August. Ermolao is also protector of the olive tree. The church keeps the relics of his left arm which was carried here from Costantinopoli in the 12th century under concession of the Byzanthine emperor Alessio I in change of military support by the Pisa Republic.
The Pisan Romanesque façade is divided by two tiers of blind arches. Decorations consist of geometric motifs that are typical of Pisan architecture. To the left of the church stands the thick, unfinished bell tower, built of stones and bricks.
The interior is divided into a nave and two aisles by granite columns topped by Ionic and Corinthian capitals. Interesting items include the altar in Carrara marble, the 17th century lesser altars, a 12th century baptismal font consisting of four basins sculpted from a single block of marble with reliefs, produced by the school of Biduino.