O'Carroll's Castle is a historic structure located in County Offaly, Ireland. It was built in the 15th century by the O'Carroll family, who were prominent Gaelic lords in the region. The castle served as a defensive stronghold and a symbol of the family's power during the medieval period. The castle features typical medieval architecture, including thick stone walls and narrow windows. Over the years, it has undergone various renovations and restorations. Today, O'Carroll's Castle is a popular site for visitors interested in Irish history and medieval architecture.