Ardgillan Castle Garden, Dublin

This 18th-century castle and garden was built by the Dean of Clonfert in 1738 and boasts superb views of the Dublin coastline and countryside. Now furnished and restored in Victorian style, Ardgillan houses a permanent exhibition of 17th-century Down Survey maps of Ireland. The garden features a conservatory and rose garden, including sections for herbs, vegetables and Irish plants. Rumors abound that there's also a ghost on the premises!