Milecastle 73

Each milecastle on Hadrian's Wall had two associated turret structures. These turrets were positioned approximately one-third and two-thirds of a Roman mile to the west of the Milecastle, and would probably have been manned by part of the milecastle's garrison. The turrets associated with Milecastle 73 are known as Turret 73A (grid reference NY30505952) and Turret 73B (grid reference NY30025961). The exact locations of the turrets have not been found. Both sites fall within Burgh Marsh where there is no evidence for any Wall structures.^[3][4]

• http://en.wikipedia.org/wiki/Milecastle 73