This is the triangulation pillar on the summit of Pendle Hill, near Clitheroe, Lancashire.
Trig pillars were built on most hill and mountain tops, and other prominent places when the triangulation network on which British mapping is based was being surveyed.
They are now largely redundant, with the advent of modern mapping methods, and the Ordnance Survey have announced that they wiil no longer maintain them.
Pendle Hill (557m) is a prominent whale-back hill in the Ribble Valley, with extensive views in all directions. On the day this shot was taken, the snow-capped Lakeland Fells, some 65 miles away, were clearly visible.