Birr Castle

Birr Castle is a historic demesne and country house in the town of Birr, County Offaly, Ireland, long associated with the Parsons family. The estate is internationally noted for its 19th-century contributions to observational astronomy.

The demesne contains formal gardens, an extensive arboretum and displays relating to the estate’s scientific history, including interpretation about the large telescope built on site in the 19th century. The grounds and visitor centre provide routes and exhibitions explaining the castle’s role in Victorian-era astronomy.

Birr Castle was the family seat of the Parsons (Earls of Rosse) and in the mid-19th century William Parsons, 3rd Earl of Rosse, constructed the massive ‘Great Telescope’ on the demesne, which used a 72-inch metal mirror and was the world’s largest telescope for several decades. The estate has been altered and restored over time but retains its historic house, gardens and scientific legacy.

The castle and demesne lie on the edge of the town of Birr in County Offaly, in Ireland’s midlands, and are accessible from regional roads and nearby towns.

• Historic telescope: Home to the 19th-century 'Great Telescope' built by the Parsons family, which used a 72-inch metal mirror and was the world's largest telescope for much of the 19th century.
• Visitor facilities: The castle demesne includes formal gardens, arboretum plantings and a science centre that presents the site's astronomical history to visitors.

What to See #

• Gardens and terraces: The restored 19th-century reflecting gardens and formal terraces within the demesne that are open to the public as part of the visitor route.
• Great Telescope: The site of the historic demonstration telescope assembled by the Parsons family; the original Great Telescope had a 72-inch speculum mirror and made Birr internationally significant in 19th-century astronomy.