Nenagh Castle is Nenagh's oldest building, and its construction in the 13th century laid the foundation for the development of the town. Theobald FitzWalter, whose successors would become Earls and Dukes of Ormond, built the castle, and upon its completion c.1220 it served as the main seat of the Butler family until 1391.

The castle boasts the finest cylindrical keep in Ireland. Like most keeps, it formed part of the perimeter of the fortress, being incorporated in the curtain walls surrounding a five-sided courtyard. The keep features four storeys. Thanks to a recent renovation, this wonderful landmark now represents the town’s premier tourist attraction.

The castle is a medieval building and has a stone spiral staircase to the top. There are 101 steps in all. Access to the tower is through a passageway within the base of the wall. This has low head room, so visitors will need to stoop to avoid hitting the stone above.

Please note: all children under the age of 16 must be accompanied by an adult. The stairs in the keep are very steep and narrow. The keep is not accessible for visitors with disabilities. There are interpretation panels on each floor of the castle which allow for self-guiding.

Entrance to the castle is located on O’Rahilly Street, and it can also be reached via Banba Square.