Russborough was built in 1741 by Joseph Leeson, the son of a wealthy brewer in Dublin.
The architect was Richard Cassells, a great promoter of the Palladian style of architecture in 18th-century Ireland. It took around 10 years to build.
Russborough is widely considered to be Cassells's finest achievement, it was also his last as he died before Russborough was completed.
It is generally acknowledged that the house was finished by Francis Bindon, a successful artist and architect from the country's mid-Georgian era.
Russborough is built of silver-grey granite which came from a quarry at Golden Hill, just outside Blessington.
The front facade is the longest in Ireland, 700ft end to end.