The patron saints of Guardea are Saint Caesarius, celebrated on 1 November, and Saint Peter, celebrated on 29 June: they are the town's ancient co-patrons, titular saints of the church of Santi Pietro e Cesareo, built in the first decades of the 18th century on the site, then called Piano Antico, where an ancient rural church dedicated to Saint Cecilia had stood. In the sacristy, in a cabinet, a silver reliquary is kept containing a bone fragment of Saint Caesarius, deacon and martyr, the work of a central Italian workshop.
The town lies at the foot of two hills, Guardea Vecchia, where the ruins of the old settlement remain, and the Poggio, where the medieval castle stands: founded as an imperial fief in 1034 on a pre-existing 7th-century Byzantine tower and built by the Normans, it is one of the oldest castles in Italy and was restored by Antonio da Sangallo the Younger in the 16th century. In the 12th century it became part of the «Status Alviani», a fief of the Church, and was conquered over time by figures such as Frederick II of Swabia, Charles V of Habsburg and Cesare Borgia, who gave it to his sister Lucrezia.
