This pentagonal fort lying close to the north bank of the Afon Vyrnwy was discovered from the air in 1986 and investigated on the ground over the subsequent three years. The defences consist of a 16½ feet (5m) wide rampart fronted by two ditches, the inner 6¾ wide, the outer 10 feet wide, each 3½ feet deep (2.05m & 3.05m by 1.05m), enclosing an area of just over 2¾ acres (2.23ha). A resistivity survey was conducted shortly after discovery and on the strength of these results excavations were carried out in fort's interior. These investigations revealed the sleeper-trenches of a timber-built granary lying close to the suspected northern gateway, also the metalling of a 4m wide via sagularis, the patrol-road which encircled the camp within the defences. The post-hole remains of a timber barrack-block were also identified.
Several Roman marching camps lie nearby to the east, most (if not, all) of which possibly predate the fort; there are three at Abertanat and another two at Clawdd Coch. It is possible that all these Roman fortifications were built in response to a stand of the Britons at the Llanymynech hillfort, which lies beyond the temporary camps to the east.