King John's Castle

King John's Castle stands on the southern tip of King's Island in the heart of Limerick city, on the banks of the River Shannon where the river narrows between the medieval city and the opposite bank. The castle was built between 1200 and 1210 by King John of England — the same John of Magna Carta fame — as a strategic fortification controlling the river crossing and the approach to Thomond, the kingdom of the O'Brien dynasty. It is one of the largest and best-preserved examples of Anglo-Norman military architecture in Ireland.

The castle's five round towers and two-storey gatehouse are largely intact. Excavations inside the courtyard in the 1990s uncovered evidence of earlier occupation — houses from a pre-Norman Viking-era settlement beneath the castle floor are visible through glass panels in the courtyard. The visitor experience includes an interactive exhibition covering the castle's history from the Viking settlement through the Norman construction, the Siege of Limerick in 1651 (when Cromwellian forces took the city), and through to the 20th century.

Limerick is a working-class city with a tourism infrastructure that punches below its historical weight — the castle, the Hunt Museum (one of the finest private collections in Ireland, now publicly accessible) and Limerick city's medieval core are genuinely worth a day. The castle sits at the junction of Thomond Bridge and the Nicholas Street approach, with good views down the Shannon. St Mary's Cathedral (12th century, free entry) is a five-minute walk across the bridge.