Geograph - photograph every grid square

A milestone is one of a series of numbered markers placed along a road, canal, railway or sometimes paths at intervals of one mile or occasionally, parts of a mile. They are typically located at the side of the route. They are alternatively known as mileposts or mile posts (abbreviated MP on maps). Mileage is the distance along the route from a fixed starting point.
Milestones are constructed to provide reference points along the route. This can be used to reassure travellers that the correct route is being followed, and to indicate either distance travelled or the remaining distance to a destination.
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