Nenagh Castle

An early 13th century castle, with a massive 30-m chess piece of a circular Donjon or Keep. It was battled over several times but never smashed, so the lower two-thirds are a fine Norman survival. The top third is a tale of "bishop takes castle, check!" In 1861 Bishop Flannery added the top level of clerestory windows and crenellations. He intended it to become the bell tower of a grand RC Puginesque cathedral, but the economic slump of the US Civil War put a check on that, and then Ennis Cathedral was developed instead. You can climb the castle's interior 101 spiral stairs to the top, but they're steep and narrow.