The property is named after the Norman knight Eust...

The property is named after the Norman knight Eustace le Poer. King James I passed the land in 1609 to Sir Richard Wingfield, whom he raised to Viscount Powerscourt. He commissioned the plant around 1730; other ornamental gardens were added in the middle of the 19th century on behalf of the 7th Viscount. Particularly interesting parts of the complex are the Italian and Japanese gardens, the outside staircase between the mansion and Lake Triton, the "Pepper Pot Tower" (a small tower from 1911) and the Bamberg Gate (a gate from the Bamberg Cathedral). Also noteworthy is the small pet cemetery, on which - for some 90 years - dogs, cats, ponies, horses and cows are buried.