Milecastle

A milecastle was a small fort (fortlet), a rectangular fortification built during the period of the Roman Empire.

On either side of the milecastle was a stone tower (turret), located about one-third of a Roman mile (500m or 540 yards) away.

A system of milecastles (known as milefortlets) and intervening stone watchtowers extended from the western end of Hadrian's Wall, along the Cumbrian coast as far as Tower 25B at Flimby,[1] but they were linked by a wooden palisade and not a wall fronted by a deep ditch, and they had no gateway through the palisade.

This system was introduced by J. Collingwood Bruce at the end of the 19th century, and became a standard around 1930, though Peter Hill has suggested that there may have additionally been a Milecastle 0.

Despite evidence of the curtain wall continuing for around a quarter of a mile west of Bowness-on-Solway, the Turrets between MC80 and MF1 are known as Towers 0a and 0b.