On top of a hill outside St. Ives in Cornwall (Carbis Bay, to be geographically precise) is this granite monument built in 1767.

It was intended to be a mausoleum for it's creator John Knill, but since he was buried in Holborn, London, it has always remained empty. Among his many minor claims to fame is that he was mayor of the town between 1762 & 1782.