The Piazza dei Miracoli (; ), formally known as Piazza del Duomo (), is a walled area located in Pisa, Tuscany, Italy, recognized as an important center of European medieval art and one of the finest architectural complexes in the world. Considered sacred by the Catholic Church, its owner, the square is dominated by four great religious edifices: the Pisa Cathedral, the Pisa Baptistery, the Campanile, and the Camposanto Monumentale (Monumental Cemetery). Partly paved and partly grassed, the Piazza dei Miracoli is also the site of the Ospedale Nuovo di Santo Spirito (New Hospital of the Holy Spirit), which houses the Sinopias Museum () and the Cathedral Museum ().
The name Piazza dei Miracoli was coined by the Italian writer and poet Gabriele D'Annunzio who, in his novel Forse che sì forse che no (1910), described the square as the "prato dei Miracoli", or "meadow of miracles". The square is sometimes called the Campo dei Miracoli ("Field of Miracles"). In 1987, the whole square was declared a UNESCO World Heritage Site.
Cathedral
The ear of the Piazza del Duomo is the Duomo, the medieval cathedral of the Archdiocese of Pisa, dedicated to Santa Maria Assunta (St. Mary of the Assumption). The cathedral has two aisles on either side of the nave. The transept consists of three aisles. The church is known also as the Primatial, the archbishop of Pisa being a Primate since 1092.
Its construction began in 1064 by the architect Buscheto. It set the model for the distinctive Pisan Romanesque style of architecture. The mosaics of the interior, as well as the pointed arches, show a strong Byzantine influence.
The façade, of grey marble and white stone set with discs of coloured marble, was built by a master named Rainaldo, as indicated by an inscription above the middle door: Rainaldus prudens operator.
The massive bronze main doors were made in the workshops of Giambologna, replacing the original doors destroyed in a fire in 1595. The original central door was of bronze, made around 1180 by Bonanno Pisano, while the other two were probably of wood. However, worshippers have never used the façade doors to enter, instead entering by way of the Porta di San Ranieri (St. Ranieri's Door), in front of the Leaning Tower, built around 1180 by Bonanno Pisano.
Above the doors are four rows of open galleries with, on top, statues of Madonna with Child and, on the corners, the Four evangelists.
Also in the façade is found the tomb of Buscheto (on the left side) and an inscription about the foundation of the cathedral and the victorious battle against the Saracens.
At the east end of the exterior, high on a column rising from the gable, is a modern replica of the Pisa Griffin, the largest Islamic metal sculpture known, the original of which was placed there probably in the 11th or 12th century, and is now in the Cathedral Museum.
The interior is faced with black and white marble and has a gilded ceiling and a frescoed dome. It was largely redecorated after a fire in 1595, which destroyed most of the Renaissance art works.
The impressive mosaic of Christ in Majesty, in the apse, flanked by the Blessed Virgin and St. John the Evangelist, survived the fire. It evokes the mosaics in the church of Monreale, Sicily. Although it is said that the mosaic was done by Cimabue, only the head of St. John was done by the artist in 1302, his last work, since he died in Pisa the same year. The cupola, at the intersection of the nave and transept, was decorated by Riminaldi showing the assumption of the Blessed Virgin.
Galileo is believed to have formulated his theory about the movement of a pendulum by watching the swinging of the incense lamp (not the present one) hanging from the ceiling of the nave. That lamp, smaller and simpler than the present one, is now kept in the Camposanto, in the Aulla chapel.
The granite Corinthian columns between the nave and the aisle came originally from the mosque of Palermo, captured by the Pisans in 1063.
The coffer ceiling of the nave was replaced after the fire of 1595. The present gold-decorated ceiling carries the coat of arms of the Medici.