Birr Castle (Irish: Caislean Bhiorra )  is a large castle in the town of Birr in County Offaly, Ireland. It is the home of the seventh Earl of Rosse, and as such residential areas of the castle is not open to the public,  although the grounds and gardens of the royal estate is available to the public.
Ireland’s Historic Science Center
The castle grounds are also home to Ireland’s historic Science Center , a museum of Ireland’s historical researchers and their contributions to astronomy and botany. 
See also: Earl of Rosse
There has been a castle on the site since 1170, and from the 14th to the 17th century O’Carroll family ruled from here over an area called “Ely O’Carroll.” 
After the death of Sir Charles O’Carroll, Sir Laurence Parsons (died 1628) was granted Birr Castle and 1,277 acres (5.2 km 2 ) of land in 1620.   Parsons dedicated English masons in the construction of a new castle on location.This construction was taking place, not in place of O’Carroll Black Tower (then disappeared) but at Gatehouse. “Flankers” was added to the gatehouse wrong on both sides, giving the castle plan retains today. 
After the death of Sir Laurence Parsons and his older son, Richard Castle passed to his younger son William.  During the Irish uprising in 1641 William besieged in Birr for fifteen months by Catholic forces. After the Civil War, William son of Laurence (baronet from 1677) restored the castle.
A later descendant, Laurence Parsons, 2nd Earl of Rosse, also engaged in some rebuilding and elevated and “Gothicised” castle in the early 19th century. In turn, his son, William Parsons, 3rd Earl of Rosse, was responsible for the construction of the large telescope at Birr. When complete in 1845, it was the largest telescope on Earth, which can capture more light and look further into space than any telescope had done before. Birr therefore became a focus for astronomical observations, and visitors came to visit the observatory from around the world – including Charles Babbage and Napoléon Eugène, Prince Imperial. 
When the 3rd Earl died, his sons carried on the scientific tradition, and the 4th Earl (Lawrence Parsons, 4th Earl of Rosse) is known to measure the heat of the moon. After his death in 1908, but fell into disrepair telescope; the mirror was taken to the Science Museum in London, and around 1914 the telescope’s metallic support structure were melted down to be used in the First World War. 1925 wooden structures around the walls torn down for safety reasons. After several attempts intermediate restoration, was the telescope restored more fully in the late 1990s. 
“The big telescope” and other functions
See also: Leviathan of Parsonstown
An important function because of the castle is “the big telescope” orLeviathan (aka The Rosse telescope ) of the third Earl of Rosse, an astronomical telescope with a 183 cm (72 inch) reflector. It was completed in 1845 and used for decades before the last observations were made during the first years of the 20th century. Its record size not surpassed until the completion of the 100-inch (2.5-meter) Hooker telescope at Mount Wilson Observatory in 1917. It was demolished in 1914, but the structure was restored and reconstructed telescope in the 1990s and is open to the public.
Laurence Parsons, 4th Earl of Rosse and his mother was a prominent photographers and her darkroom, which is also on show, are believed to be the oldest surviving example in the world.
The grounds of the palace contains the oldest wrought iron bridge in Ireland, dating from the 1820th 
The walled gardens in the grounds of the boxwood hedges that are over 300 years old. They are also, according to The Guinness Book of Records , the tallest hedge in the world. 
The Irish entry to the 2014 European Tree of the Year contest was Birr Castle Grey Poplar (poplus x canescens). Unfortunately, February 12, 2014 while voting was still open, it was blown down in a storm.
- Jump up ^http://www.ingeniousirelandonline.ie/ga/resources/resource_visit_01.htm
- Jump up ^ The Birr scientific and Heritage Foundation. “Birr Castle”.BirrCastle.com. Archived from the original September 21, 2008.
- Jump up ^ The Birr scientific and Heritage Foundation. “Ireland’s Historic Science Center”. BirrCastle.com. Archived from the original September 18, 2008.
- Jump up ^ The Birr scientific and Heritage Foundation. “Birr Castle Grounds”. BirrCastle.com. Archived from the original January 21, 2008.
- ^ Jump up to: abc The Birr scientific and Heritage Foundation. “Birr Castle, Co. Offaly. “. Archived from the original August 7, 2008.
- Jump up ^ Lundy in 2011, citing i15200: Mosley 2003, p. 1327
- Jump up ^ The Birr scientific and Heritage Foundation. “Birr Castle Demesne, discovery: genealogy”. Retrieved March 2012. Check date values in: (help) | Access-date =
- Jump up ^ Detail of telescopic Reconstruction
- Jump up ^ The Rough Guide to Ireland, 9th Edition; p 219 ISBN 978-1-85828-056-1
- Jump up ^ The Box Hedge
- Lundy, Darryl (27 August 2011). “Sir Laurence Parsons”.
- Mosley, Charles, ed. (2003). Burke’s Peerage, Barone & Knightage (3 volumes). 1 (107th ed.). Wilmington, Delaware, USA: Burke’s Peerage (Genealogical Books) Ltd. p. 1327th