The untarnished historic centre is surrounded by magnificent defensive walls even today. It tops the Cerruglio hill, which gives its name to the town's symbolic Cerruglio fortress.
The fortress was built between the fourteenth and sixteenth centuries, centring around a semicircular main tower and two square auxiliaries, the Torre dell'Apparizione and the Torre di Santa Barbara. Together, they form a hefty triangular stronghold. The Torre dell'Apparizione takes its name from an old legend, which maintains that in 1400 the Madonna del Soccorso appeared on the walls and defended the fortress from the attacking Pisan forces.
If you walk the circuit of the walls, you will see the surviving three of the original fifteen city gates. The most important of these is the Porta Fiorentina, which sets you on the road for Florence; the Porticciola points towards Lucca, while the Porta Nuova leads south.
In the old centre, it is worth visiting the collegiate church of Sant'Andrea, which was originally built in the first half of the sixteenth century but was later restructured in the eighteenth. Have a look also at the small, delightful Teatro dei Rassicurati, where Giacomo Puccini often dropped by.
The parish church of San Piero (sometimes called San Piero in Campo) stands at the foot of the Cerruglio Hill. This church can claim to be one of Tuscany's oldest, with origins in the earliest days of Christianity.