The world's first ever water powered cotton mill, built by Richard Arkwright and now under extensive renovation by The Arkwright Society. The original spinning mill can be seen in the lower left-hand corner of the square, plus a later round-ended extension which was said to be a fortification against the machine-breaking "Luddites".
Wikipedia article:
http://en.wikipedia.org/wiki/Richard_ArkwrightCategory:
interesting place