Birr Castle, located in County Offaly, has a long and distinguished history dating back to 1170, when the original stronghold was established. From the 14th to the 17th centuries, it served as the seat of the O’Carroll dynasty, who ruled over the region then known as Ely O’Carroll.

Following the death of Sir Charles O’Carroll, the estate was granted to Sir Lawrence Parsons in 1620. Parsons received Birr Castle along with 1,277 acres of surrounding land. Rather than rebuilding on the site of the O’Carrolls’ now-lost Black Tower, he began constructing a new castle at the original gatehouse, adding diagonal flanking towers that define the castle’s current layout.

After Sir Lawrence’s death, and that of his elder son Richard, the estate passed to his younger son, William Parsons. During the Irish Rebellion of 1641, William withstood a 15-month siege at what was then known as Parsonstown (modern-day Birr). Later, William’s son Laurence—who was created a baronet in 1677—refurbished the castle after the conflict.

Significant changes came again in the early 19th century under Laurence Parsons, 2nd Earl of Rosse. He undertook a major renovation, heightening the structure and adding Gothic Revival elements. His son, William Parsons, the 3rd Earl of Rosse, was a pioneering astronomer. In 1845, he completed construction of the “Leviathan of Parsonstown”—then the largest telescope in the world. This achievement turned Birr into a center for astronomical study, drawing visitors and scientists from around the world, including Charles Babbage and Napoléon Eugène, Prince Imperial of France.

The scientific legacy continued with the 4th Earl of Rosse, Lawrence Parsons, who is noted for measuring the heat of the Moon. After his death in 1908, the telescope fell into decline. The mirror was transferred to the Science Museum in London, and around 1914, the metal components were scrapped for use during the First World War. For safety reasons, the remaining wooden structures were removed in 1925.

Restoration efforts were attempted throughout the 20th century, but it wasn’t until the late 1990s that the great telescope was more fully restored to its former glory.

In 2025, Birr Castle—alongside Dunsink Observatory and Armagh Observatory—was added to Ireland’s World Heritage Tentative List as part of the Historic Astronomical Observatories group, marking a major step toward potential UNESCO World Heritage status.

Although it nowhere near as notorious as Leap Castle, staff have acknowledged “unusual activity” at Birr Castle. Staff and visitors have reported sightings of shadowy figures and spoken of unexplained occurrences, particularly in certain older parts of the estate. If anyone would like to add further detail, please Submit an Amendment or Add Your Experience.