Alatri

The Acropolis of Alatri, made up by the most internal of two rings of polygonal walls, with five doors of which two are still in function, is the most grand and best conserved complex in all of Italy. Even a discrete portion of the external ring remains pretty much intact.  The polygonal walls are made up of enormous dry masses one next to the other, dry in the sense that being laid without mortar, with amazing precision if you think of the technical means in existence at the time. The concept was that the masses had to be sufficiently large and heavy to not be displaced by attacks, given that mortar had still not been invented and that cementing them would make the wall completely joined.
The era is uncertain in that four different styles have been pinpointed that range from the 6th to 2nd-1st centuries B.C.; little by little the masses take on an irregular form passing to a more square shape, but all, however, precede the Roman conquest. The walls of Alatri are among the oldest, and a part of the first and second styles are work of the Hernici, ancient Italian people who were the first to inhabit the site. Naturally, some of the portions were demolished in occasions of war and were then reconstructed.
Aletrium, this was the name of the town at the time of the Hernici, became a Roman municipium in 90 B.C. after some time as a federated city of Rome. In the era of Constantine it was a diocese and in 547 the bishop's headquarters; Totila conquered it with great destruction, but it rose again with the name Civitanova. With the fall of the Empire, religious authority became the only one. In a commune era, the city enlarged its own sovereignty on the surrounding lands and vigorously defended its own independence during the fighting between the Empire and the Papacy. Notable prosperity was enjoyed in these years, and important buildings were constructed that even today characterize the beautiful historic center.