The town stands on a tuff rock ringed by natural ditches, on the slopes of the Baccano valley, which is an ancient volcanic lake, later drained. To the Etruscans is owed the tagliata of the seventh century before Christ, a gorge cut by hand to link that valley with the lake of Martignano. On the top of Monte Razzano the Romans raised a small temple to Bacchus, and from it comes the name ad Baccanas given to the valley; along the via Cassia, right beside the road, rose the mansio ad Vacanas, that is a posting station. Built in the first century after Christ over republican structures, it had an area for the traveller's rest, with baths and shops, one for the care of the horses, with stables and sheds, and one for public business, with the soldiers' barracks, the market square and a portico with a fountain.
The same road, centuries later, was the via Francigena, and the mansio remained a stopping place: in the itinerary of Sigeric, archbishop of Canterbury, returning from Rome about 990, it appears under the name of Bacane as the third stage out of the city. Between the eighth and ninth centuries the popes created in the emptied Roman countryside the domuscultae, mixed-farming estates meant to recolonise, defend and administer the land; when that system fell, the people of the scattered villages moved onto the rock and began to fortify it. Campagnano appears for the first time in a document of 1076, as a castellum. In 1270 a statute was agreed between the people and cardinal Riccardo Annibaldi: it is one of the first statutes of the Roman Campagna. In 1410 the senate of Rome sold the town to Gentile Orsini, and with the Orsini began its best period, with great changes to the town's fabric and, in the fifteenth century, the stays of popes, cardinals and nobles. Today, where horses were once changed, stands the Vallelunga racing circuit.
