A landscape Architect student showed me this website that the university pays for, so they can use maps that date back to the early 1800's. The maps reveal ancient ruins of Roman Villas, Iron Age settlements, burial sites, stone monuments, and caves. The maps also reveal the town plans in the urban areas too, which reveal how the housing and the towns were planned out in relation to an industrial landscape during the mid 1800's. The maps can be used to find ruins or old buildings and marked down, tracked down and photographed/ re-photographed, this re-photography can be used to re-invent history, or to re-imagine history. You could also use them to study the change in the landscape, wether thats in the countryside of in an urban setting, see what gets covered over and what is looked after, listed buildings for example.
"Historic Digimap delivers historical Ordnance Survey maps of Great Britain. The Collection is licensed from Landmark Information Group for UK Higher and Further Education."
Historic Digimap offers the following map images, the originals of which were published between 1846 and 1996: