High above the River Blackwater, this turreted medieval fortress dates from 1185, when Prince John of England (later the infamously bad King John who signed the Magna Carta) established a castle on this site. The grounds, surrounded by thick defensive walls dating from 1626, are spread across nearly 3 hectares (7 acres). They’re peaceful and quite lovely to walk around, dotted with sculptures and with views of the massive castle (which is, sadly, not open to the public). Also on the grounds is Lismore Castle Arts (www.lismorecastlearts.ie; 058/54061), a gallery devoted to contemporary visual arts, with a good program of exhibitions. Big name artists featured here have included Ai Weiwei and Dorothy Cross. Entry is included in the price for the gardens. The gallery has opened a second space at St. Carthage Hall, located on Chapel Street in Lismore (058/54061), open Friday to Sunday noon to 5pm, during exhibition periods only (call or go online to check the schedule). Admission is free.