Pisa (pē´sä), city (1991 pop. 98,928), capital of Pisa prov., Tuscany, N central Italy, on the Arno River. It is now c.6 mi (9.7 km) from the Tyrrhenian Sea, which once reached the city. Pisa is a commercial and industrial center; manufactures include auto and truck parts, glass, pharmaceuticals, and processed food. Probably a Greek colony, later certainly an Etruscan town, it became a Roman colony (180 b.c.) and prospered. During the 9th to 11th cent. a.d. it developed into a powerful maritime republic, fighting the Arabs throughout the Mediterranean and rivaling Genoa and Venice. Pisa's political and commercial power increased upon acquisition of possessions and trading privileges in the eastern Mediterranean during the Crusades.
While competing with Genoa for the possession of Corsica and Sardinia, Pisa was crushed by the Genoese in the naval battle of Meloria (1284). As a Ghibelline center in the 13th and 14th cent., the city was also chronically at war with Florence, to which it fell in 1406. At the same time, a school of sculpture founded by Nicola Pisano flourished in Pisa and gave the city some of its great art treasures. The Council of Pisa met there in 1409. The university (founded in the 14th cent.) enjoyed a great reputation during the Renaissance; Galileo, who was born in Pisa in 1564, was a student and later a teacher there. Pisa was badly damaged in World War II but was extensively reconstructed after 1945, largely retaining the characteristic Pisan style, a variation of the Romanesque.
The most famous of Pisa's many landmarks is the marble Leaning Tower (180 ft/55 m high). Begun (1173) as the bell tower for the cathedral of Santa Maria Maggiore, it started to list when three stories high, and attempts to compensate for this during construction (which was stopped several times by war) have given the tower a slightly curved shape vertically. By the 1990s the tower was tilting more than 13 ft (4 m) from vertical, and in 1993 it was shored up with 660-ton (600-metric-ton) lead counterweights. In 1995 steel cables attached to an underground platform were installed to further correct the problem, but only by gradually removing earth from underneath the tower was the tilt reduced to about 11 ft 8 in. (3.56 m) in 2001. The present restoration is predicted to preserve the tower's stability for some 300 more years.
The city's other noteworthy structures include the celebrated Pisan Romanesque cathedral (1068-1118), which has a fine marble facade, bronze panels by Bonnano Pisano, and a pulpit by Giovanni Pisano (reconstructed after a fire in 1926); the marble baptistery (1153-1278); the Camp Santo (cemetery), with frescoes of the 14th and 15th cent. (many badly damaged in World War II); and the churches of Santa Maria della Spina (early 14th cent.) and Santa Caterina. Nearby the city is the Carthusian Monastery of Pisa, with large classical cloisters.