Where the Romanesque church of S. Pietro in Vinculis now stands there was once a pre-existing church, mentioned for the first time in 763 AD. The Romanesque Church of San Pietro (known by locals as S. Pierino), is one of three Pisan churches (the others are S. Cristina and S. Margherita, the latter no more existing) documented in Longobard times.
The church was consecrated in 1118, built in stone blocks. The plan was for a two-story building: the Church was raised above street level and a crypt below with cross-vaulting resting on stone columns, later used for burial, as funeral inscriptions carved on the columns testify.
The façade is divided into two levels. The lower decorated with five dead arches separated by rose windows and rhombs: the main door is decorated with a carved lintel, pilasters and capitals. The upper story has three arches and a central mullioned window. The slit windows of the crypt are at pavement level. The belfry, originally a house, is in an adjacent tower.
The interior is separated into three aisles by a double row of six columns and two pilasters decorated with Romanesque capitals. On the floor is a 12th century mosaic of coloured marble. Church and crypt have recently been renovated.
Until Pisa was conquered by Florence, an important document was guarded in this Church: Giustinian I’s Digesto, the text of the Corpus Iuris Civilis, known as “Pandette Pisane” (today at the Biblioteca Medicea Laurenziana in Florence).