When Lucy Honeychurch, the heroine of EM Forster's A Room With a View, is stranded in Santa Croce without a Baedeker, she first panics and then, looking around, wonders why it's thought to be such an important building. After all, doesn't it look just like a barn ('a black and white facade of surprising ugliness')?

On entering, many visitors to this massive Franciscan basilica share the same reaction. The austere interior can come as something of a shock after the magnificent neo-Gothic facade, which is enlivened by varying shades of coloured marble (both it and the campanile are 19th-century additions). The church itself was designed by Arnolfo di Cambio between 1294 and 1385 and owes its name to a splinter of the Holy Cross donated by King Louis of France in 1258.

Though most visitors come to see the tombs of famous Florentines buried inside this church - including Michelangelo, Galileo, Ghiberti and Machiavelli - it's the frescoes by Giotto and his school in the chapels to the right of the altar that are the real highlights. Some of these are substantially better preserved than others - Giotto's murals in the Cappella Peruzzi are in particularly poor condition. Fortunately, those in the Cappella Bardi (1315-20) depicting scenes from the life of St Francis have fared better. Giotto's assistant and most loyal pupil, Taddeo Gaddi, frescoed the neighbouring Cappella Majeure and nearby Cappella Baroncelli (1332-38); the latter takes as its subject the life of the Virgin.

Taddeo's son Agnolo painted the Cappella Castellani (1385) with delightful frescoes depicting the life of St Nicholas (later transformed into 'Santa Claus') and was also responsible for the frescoes above the altar.

From the transept chapels a doorway designed by Michelozzo leads into a corridor, off which is the Sagrestia, an enchanting 14th-century room dominated on the left by Taddeo Gaddi's fresco of the Crucifixion. There are also a few relics of St Francis on show, including his cowl and belt. Through the next room, the church bookshop, you can access the Scuola del Cuoio, a leather school where you can see the goods being fashioned and buy the finished products. At the end of the corridor is a Medici chapel with a fine two-tone altarpiece in glazed terracotta by Andrea della Robbia.

Brunelleschi designed the second of Santa Croce's two serene cloisters just before his death in 1446. His unfinished Cappella de' Pazzi at the end of the first cloister is notable for its harmonious lines and restrained terracotta medallions of the Apostles by Luca della Robbia, and is a masterpiece of Renaissance architecture. It was built for, but never used by, the wealthy banking family destroyed in the 1468 Pazzi Conspiracy - when papal sympathisers sought to overthrow Lorenzo il Magnifico and the Medici dynasty.

Located off the first cloister, the Museo dell'Opera di Santa Croce features a Crucifixion by Cimabue, restored to the best degree possible after flood damage in 1966, when more than 4m of water inundated the Santa Croce area.

Other highlights include Donatello's gilded bronze statue St Louis of Toulouse (1424), originally placed in a tabernacle on the Orsanmichele facade; a wonderful terracotta bust of St Francis receiving the stigmata by the della Robbia workshop; and frescoes by Taddeo Gaddi, including The Last Supper (1333).