Milecastle 25 is believed to be a long-axis milecastle with unknown gateways type. Such milecastles were thought to have been constructed by the legio VI Victrix who were based in Eboracum. The milecastle measured across, and had broadeast and west walls. The north gateway and wall are beneath the road. There are possible traces of a milecastle ditch to the south, but no traces of a spur from the Military Way despite evidence of causeways over both the ditch and vallum ditch at this point.
Excavations and investigations
1930 - The location was established. Excavations by T Hepple established the width thickness of the side walls.
1966 - English Heritage Field Investigation. It was noted that the remains consisted of a low mutilated grassy platform, with superficial traces of a ditch on its south side.
Associated Turrets
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 25 are known as Turret 25A and Turret 25B.
Turret 25A
Turret 25A is probably located slightly to the east of Hill Head Farm. Although located in 1930 by T Hepple, trenching in 1959 failed to relocate the turret. It was concluded that a scatter of large sandstones had been mistaken by Hepple for the turret's wall. Location on Ordnance Survey 1:25 000 map:
Turret 25B
Turret 25B is located to the south west of St Oswald's Church at Heavenfield, and no visible remains exist. It was first excavated in 1930 by T Hepple,. Three to four courses of the South face were discovered. Further excavation took place in 1959. Its internal dimensions were found to be and . The north wall was found to be thick, with the remaining walls being thick. Its construction is of a type generally associated with Legio XX Valeria Victrix but no evidence was found for an occupation later than late Antoninus Pius period. Sherds from as many as fifty flagons were also found, along with more amphora sherds than would be expected. Five gaming pieces were found outside the North-West corner of the turret, possibly indicating the existence of a window in the west wall. Further objects of copper and iron, including an arrowhead, were found. The walls were constructed with mortar. The floor was constructed from clay containing mortar, and there were dumps of this substance found outside the walls. The internal south-west corner was marked off by boulders as a working area, with a hearth. A platform was later added against the south wall. A path led from the turret, with traces of a wall evident on its left. Location on Ordnance Survey 1:25 000 map:
