The first documented settlement was in a locality called Marruto and from there the inhabitants moved and founded the castle, called Castello del Poggio, in about 1035. In the 12th century a descendent of Count Baschi della Guascogna founded on the hill overlooking the present town, a castle to guard the territory. The origin of the name, from the German word "wart" (guardian), demonstrates that Guardea started as a "protective lookout". In the 13th century the castle became the property of the Lords of Alviano who held it until 1581 when Caterina Cervara, Bartolomeo d'Alviano's grand-daughter, brought it as her dowry to her husband Ludovico di Marsciano. Subsequently the inhabitants moved further down the valley, to the present day site of Guardea, and from that moment it became part of the Papal States until annexation into the Kingdom of Italy (1860). ART AND CULTURE
The oldest traces of human habitation in the area come from the Paleolithic period, as proved by tools and numerous flint chips preserved in the premises of the Archaeological Group. The Megalithic walls (in the locality of Fossi) are of interest as they date from the 3rd to 2nd century BC: the imposing walls are the ruins of a system used to embank the Tiber River and other small rivers to protect agricultural land. On the hill behind the town are the remains of the ancient castle of Guardea Vecchia: still largely visible is the scheme of eight towers (six quadrangular and two semicircular) and the large central keep. Almost directly in front of Guardea Vecchia is the Castello del Poggio, an ancient defence system that has remained unchanged over the centuries. It has been accurately restored and is now the Italian headquarters of the Club of Budapest, an international body concerned with the development of a universal civic conscience. In the town, on the elegant Piazza Panfili, stands the Parish Church from the 18th century that contains the mortal remains of Beato Pascuccio, patron saint. Next to the school, in the middle of a large park, rises the Arch of Planetary Consciousness set with rocks sent by mayors from cities all over the world. In the vicinity, just outside Guardea, are the ruins of the church and hermitage of Santa Illuminata (from the year 1007): close by is the cave that Saint Francis used as a retreat to pray and where he slept on a travertine slab that is still today venerated.