During the Roman army's conquest of Northern Britain towards the end of the first Century, a small timber fort was built here to house a garrison of 200 men. It was soon abandoned, but the site was redeveloped early in the 2nd Century AD. The fort was demolished and a second one built in stone on an artificial platform which is still just visible. It housed a cohort of 500 infantrymen.
Archaeological excavations by R.G. Collingwood between 1914 and 1920 revealed the remains of the fort's defences, and parts of the internal building arrangement, including the main gate, the south gate, the commanding officer's house, the headquarters building and the granaries, all of which may be seen today.