Broadway Tower, Worcestershire

The "Saxon" tower was the brainchild of Capability Brown and designed by James Wyatt in 1794 in the form of a castle, and built for Lady Coventry in 1798–99. The tower was built on a beacon hill, where beacons were lit on special occasions. Lady Coventry wondered whether a beacon on this hill could be seen from her house in Worcester — about 22 miles (35 km) away — and sponsored the construction of the folly to find out. Indeed, the beacon could be seen clearly.

Photo credit Newton2, via Wikimedia.