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Photo: Anna Maria 4574, CC BY-SA 4.0 via Wikimedia Commons
The mansion may be from the 16th century but was made-over in the 1840s; it's not open to tour. You come for the extensive riverside gardens, planted by William Robinson (1838-1935). He opposed the stiff formal Victorian look, and championed cottage and "wild" gardens with native species in natural places. He'd have to avert his eyes from the masses of rhododendron and the Giant Redwood planted after the victory at Waterloo.
Altamont House is a historic building best known for its ornamental gardens in County Carlow. The Robinsonian-style gardens are often referred to as "the jewel in Ireland's gardening crown".
© OpenStreetMap contributors
Fortified mansion built in 1625 astride the Dublin to Wexford road. It's a plush Georgian and Victorian interior, visit by guided tour and available for B&B. It was the location for the 1975 Stanley Kubrick film Barry Lyndon and has extensive gardens. A 19th century turbine down by the river supplied the house with electricity. The basement is the global headquarters of "The Fellowship of Isis", founded in 1976 at the dawning of the Age of Aquarius, the Age of Aquarius, A-quar-i-us! It aims to, um, "help the Goddess actively in the manifestation of Her divine plan" and apparently this is coming along nicely.
Hill fort with three concentric stone ramparts, Bronze Age circa 1000 BC, with an inner fourth wall of 15 m diameter added in early medieval times.