Birr Castle has been home to the Parsons family since the 17th century, but the main draw for visitors is the demesne: gardens, parkland, the science centre, and the great telescope known as the Leviathan of Parsonstown.
Completed in 1845, the Leviathan was the world's largest telescope until 1917. It was not a decorative eccentricity; it helped astronomers understand that some nebulae were distant star systems. The science centre also covers early photography, engineering, and the practical brilliance behind the telescope's huge mirror.