Built by the O’Donnell chieftain in the 15th century, Donegal Castle has extensive 17th century additions. It is furnished throughout and includes Persian rugs and French tapestries. Information panels chronicle the history of the Castle owners from the O’Donnell chieftains to the Brooke family.

On nearby Lough Eske there is a tiny island on which the ruins of what was a prison the O’Donnells kept their prisoners in. All that remains is one wall and even that is mostly hidden by the trees that now fill the tiny island.