Tullynally Castle, near Castlepollard about 24 km north of Mullingar, is the largest inhabited castle in Ireland — a vast Gothic pile that grew by accretion from the 17th to the 19th century, ending up with towers, battlements, and a silhouette that makes it look almost theatrical against the Westmeath sky. The current building owes most of its character to early 19th-century remodelling by Francis Johnston.
The walled gardens and the woodland arboretum are the main draw for most visitors: the grounds contain an extraordinary collection of trees, including mature specimens of species rarely seen in Ireland, planted and tended by successive generations of the Pakenham family. The gardens open in summer — check the website for current season dates as opening hours vary from year to year. Castlepollard itself is a pleasant village with a good pub, making an easy combination for a half-day trip from Mullingar. The castle is not open for interior tours.