Blythe's Folly, near Kinglassie, Fife.

Not really a Folly though as it was built by a local linen factory owner who used to spy out the linen boats sailing up the river Forth and rush to meet it for favourable purchases. During WW2 it was used as a lookout by the Home Guard.
Spotted from Loch Leven. Roy had its history at his fingertips.