The Castelli Romani owe their toponym to the fortifications built on the heights of these places by various Roman baronial families, fortifications which have however been destroyed or modified and transformed into summer residences. The only truly completely preserved fortification in the area is represented by the walls of the Abbey of San Nilo in Grottaferrata, while among the numerous patrician residences the following are worth mentioning:
• Ville Tuscolane in Frascati
• Palazzo Chigi in Ariccia
• Palazzo Papale and Secret Garden in Castel Gandolfo
The territory of the Castelli Romani is also one of the richest areas of archaeological finds in the province of Rome:
• the ruins of Tusculum in Monte Porzio Catone
• the archaeological circuit of the Castra Albana in Albano
• the Ship museum and temple of Diana Nemorense in Nemi
• the Mithraeum of Marino in Marino
• the Villa of Domiziano in CastelGandolfo within the Secret Garden
• Monte Cavo and Palazzolo in Rocca di Papa
