Powis Castle ~ Wales, UK. Built in the 13th century as a fortress for Welsh princes, Powis Castle, Welshpool, now boasts glorious terraced gardens, constructed in the 17th century.
Killarney National Park - the oldest Ireland castle gardens
Drummond Castle, One of the Finest Formal Gardens in Europe | Amazing Snapz
Alnwick Castle Gardens - Alnwick Northumberland, England