Birr Castle Demesne
Birr Castle is home to the world famous Leviathon, the Great Telescope. It was completed in 1845 and was used for several decades before the last observations were made in the first years of the 20th century. Its remained the largest telescope in the world until 1917. It was dismantled in 1914, but was restored in the 1990s and is open to the public.
For more information see http://www.birrcastle.com.
