Acropolis of Alatri

The Acropolis of Alatri in Lazio, central Italy, features some of the finest Cyclopean polygonal masonry in the Mediterranean, with walls rising over 15 meters high built from precisely interlocking megalithic blocks without mortar. Attributed to the Hernici people, the fortification dates to approximately the 6th century BC and is enclosed by a second outer wall stretching over 2 km. The acropolis plan mirrors the constellation Gemini, and UNESCO considers it "the most spectacular example of the use of geometry and astronomy in planning". Alatri fell to Rome in 306 BC.