Just before you reach Allonby, on the B5300 road from Maryport, there is a car park on your right hand side. From this car park both Milefortlet 21 and the Crosscanonby Salt Pans are accessible. Milefortlet 21 is the only portion of Hadrian’s coastal defences of the north west frontier to have been completely excavated.
This excavation, with the help of 150 Earthwatch volunteers, took two summers (approximately 20 weeks) to complete. Housed at The Senhouse Roman Museum, which is in Maryport, there are approximately 1000 pieces of pottery and iron that were recovered from this site through constant cleaning and 3D recording. There is also a reconstructed model which shows how this fortress once looked.