Town in the province of Rome, located on a tuff spur, at short distance from the Italian capital city, Zagarolo has ancient origins: in fact, the area seems to be inhabited since the period of the Roman monarchy and became shelter for the exiles of Gabi, after being destroyed by Tarquinius Superbus. It shared the historical events and the fate of the nearby city of Rome and, after the fall of the Roman Empire, it became easy prey of the barbarian invasions. First documented mention is of 970, when Pope John XIII assigned the town in fief to his sister Stephanie and her Family Counts of Tuscolana. The town was ceded to the Colonna Family, who ruled till 1043, when Marzio Colonna, covered of debts for the renovation of the town, was forced to sell the Duchy to the Ludovisi, who subsequently ceded their rights to the Rospigliosi.

Sites of Interest:
- the remains of a Roman cistern on the hill Mainello and a Roman villa in the district of Palazzolo;
- the Tondo, a Roman ludus, where the gladiators used to train;
- the Palazzaccio, a square building with corner towers, located in the area Colle Villa;
- the portico of Via Antonio Fabbrini, under which was located a public weighing machine, an oven, a slaughterhouse and a public warehouse, controlled at the time by the authorities of the Duchy;
- Palazzo Rospigliosi, which stands where once was located the medieval castle. It was transformed from military garrison to a noble residence, beautifully decorated and painted by the most illustrious artists of the Mannerism style. Today it is seat of a famous Toy Museum;
- Porta Rospigliosi and Porta San Martino;
- the Cathedral of San Lorenzo, built in 1607 by Duke Marzio Colonna and completed by the Ludovisi. It features a Latin cross plan with seven altars, and despite the losses suffered during the Second World War and the violent earthquakes, it still preserves a heritage of full respect;
- the Church of the Annunciation, built by Pompeo Colonna in 1580 and designed by Gian Lorenzo Binago. The church, built on a rock of tuff stone, features a Latin cross plan with a circular dome and an octagonal shape Bell tower. The portal is flanked by two granite columns surmounted by capitals (probably Roman remains);
- the Sanctuary of Santa Maria delle Grazie, inside which is preserved a XIII century image of Our Lady of an unknown artist, which is object of fervent devotion;
- the Cathedral of St. Peter the Apostle, built in the XVIII century on the site of an older XII century church, which had become too small to meet the needs of the growing population. The project was entrusted to architect Nicolo Michetti and continued by the architects of the family Rospigliosi, Ludovico Rusconi Sassi and Gerolamo Caccia. It is in Baroque style and features an elliptical dome.