Discovered from the air in 1991 and surveyed over the winter of 1991/2, this fort is situated on the south bank of the River Aire, a tributary of the Humber, about 8 miles east of the fort at Castleford and about the same distance north-east of the fort at Burghwallis. There are no known roads in the immediate area, which has led archaeologists and historians to speculate that the fort was intended to control river traffic and was itself supplied along the Aire.
In plan the fort has a classic rectangular, "playing card" shape outlined by a defensive system comprising a rampart and double ditch, and is seemingly aligned to the north-east across the River Aire. Within the ramparts the fort measures 416 feet from NE-SW by 348 feet transversely (127 x 106 m), giving an occupation area of around 3¼ acres (c.1.34 ha), sufficient space to have housed a five-hundred strong auxiliary infantry unit, or cohors peditata quingenaria.
Magnetometric survey conducted shortly after the fort's discovery confirmed the outline of the defences shown on aerial-photographs, and also revealed several linear features within the fort's interior, the internal road system and a number of storage pits. The ditches teminate with so-called "parrot-beak" inturnings at the gateways, several examples of which have been identified at known Agricolan encampments in Scotland, and the fort is thought on this basis to belong to the first century.