Ad Pirum was a Roman fortress. It was active during the time of the late Roman Empire. It is located on the Hruà ¡ica Plateau in southwestern Slovenia, in the hamlet of Hruà ¡ica in Podkraj. It was built in the 320s.
Excavations reveal the fortress to have an oval shape, in length, in width, and with a wall at a height of 6âÂÂ8 m and a thickness of about 2.7m; the wall towers were 10 m high. This structure represented a major fort of the Claustra Alpium Iuliarum. Claustra Alpium Iuliarum is a network of forts and walls built to secure Roman Italy from eastern invasions. It also guarded the road between Roman Italy and Pannonia. It was typically manned by 500 soldiers.