The Palazzo Rospigliosi, in the city centre, occupies the site of an ancient medieval castle, which is first referenced to when Pope Paschal II destroyed Zagarolo in the early 12th century after the rebellion of the Colonna family, of which the palace was one of the strongholds.

In the 16th century, the Colonnas and the papacy started having peaceful relations, and Zagarolo became a duchy, hence the Palace became known as Palazzo Ducale.

Here in 1606 Caravaggio created masterpieces for the Colonna family, in exchange for refuge on his journey to Naples, between Zagarolo and Paliano he executed the Supper at Emmaus, Mary Magdalen in Ecstasy and perhaps Saint Francis in Prayer.

In 1668, when the Rospigliosi acquired the duchy of Zagarolo, the Palace became their property, and was later in possession of the Pallavicini family, until it was sold to the comune in 1979.

The first gate to be encountered entering the city centre from the southeast is Porta Rospigliosi, decorated with bas-reliefs in the 16th century and Roman busts and theatrical masques.

The other gate, at the northwest entrance to the city is Porta San Martino, named in honour of Pope Martin V (Oddone Colonna).

The Museum offers a social reconstruction of toys and the act of playing in a series of sections that, through a historic excursus, crosses the fundamental periods of the 20th century.

The northern and southern limits of Zagarolo are marked by two important ancient Roman roads that are today still in use, the Via Praenestina to the north and the Via Casilina to the south.

Zagarolo has a main train station, 2 kilometres from the city centre, that connects the town to Rome, Ciampino, Frosinone, Caserta and Cassino.