Fullers Folly is located south-east of the Desmond Castle. The man behind the construction of Fullers Folly was William Fuller Hartnett born in 1804.

Tragically his wife died at the age of forty leaving him with a young family to rear. It was noted that fuller was a very close friend of Daniel O'Connell, but later on he switched his political allegiance to the 'Young Ireland'.

In 1840 he was imprisoned for a few months for his strong radical opinions. Fullers Folly itself bears the inscription of its erection dating 1889 and although record states that Fuller had leased land beside the castle from the Earl of Devon in 1867.

It is believed that Fuller had a disagreement with the Castle Authorities and as a result built this castle as a form of revenge or a hint to them.

It was a costly structure with little or no use, hence 'Folly'. Fuller died in 1879, and was buries in Churchtown graveyard, but the Folly lives on.