The Church, built from locally quarried stone and lit by slit windows, is octagonal in shape with a pyramidal cone-shaped roof resting on a central raised drum.
In 1138 this Church is mentioned as part of a construction belonging to the Knights Hospitaliers of St. John of Jerusalem, who arrived in Pisa in 1113. It later belonged to the Knights of Malta until, in 1817, the Order was suppressed and the Church passed under Royal patronage.

An inscription at the base of the bell-tower tells us that the architect was Diotisalvi, who designed the Baptistery, but restoration work in 1970 uncoveredan earlier octagonal building on which the eight pillars of this temple rest. In the 16th century a porch in sandstone was added to the church, that was already closed in by later buildings.

Towards the end of the 18th century, it was decorated with stucco mouldings but was closed in 1848 because unsafe. In 1876 it was re-consecrated, following much repair work under Rodolfo Castinelli, who restored it to its original level and dismantled the porch; at the same time the square was re-designed by Pietro Bellini, who created the metal balustrade surrounding the church.

The bracket carved with a man’s head, the rings carved with foliage and the lions’ heads over the north door are 12th century, while the bust of Diotisalvi over the west door dates from 1859. Inside is the gravestone of Maria Mancini Colonna, niece of Cardinal Mazzarino, and a well with bucket said to have been used by St. Ubaldesca to cure pilgrims in the adjacent hospital.