The Castle can be visited
Nenagh Castle

In County Tipperary, Ireland, Nenagh Castle is a castle ruin distinguished by its prominent round tower. This tower is among the best-preserved of its kind in Ireland and shapes the townscape of Nenagh.
History+
Around the year 1200, Theobald Walter, the first Baron Butler, began the construction of Nenagh Castle. His son, Theobald le Botiller, completed the complex around 1220. The castle served as the principal seat for the Butlers, who later became the Earls of Ormond, until it was moved to Kilkenny Castle in 1391. The last Marquess, James Butler, passed away in 1997 without a male heir, causing the marquessate to become extinct, while the earldom is dormant.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 52.8650, -8.1981