As majestic as it is unexpected, Birr Castle stands in the heart of Birr, an elegant town in County Offaly. Behind its neo-Gothic silhouette lies a private home still occupied by the Parsons family, surrounded by an estate of 120 acres, or almost 49 hectares.
Yet a visit offers far more than views of the castle from its gardens. Birr Castle Demesne is home to a remarkable botanical collection, a centre dedicated to the history of science, a modern observatory and, above all, the famous Leviathan of Parsonstown, which was the world’s largest telescope for more than 70 years.
Birr Castle remains the residence of the Parsons family, holders of the title Earl of Rosse. Its interior is therefore not freely accessible and is not included in the general admission ticket.
Seasonal guided tours, however, offer visitors the chance to explore five of the castle’s principal reception rooms. The tour showcases furniture, works of art, family archives and the many objects bearing witness to four centuries of the Parsons family’s presence in Birr.
In 2026, these interior tours run from 15 May to 5 September, Monday to Saturday. As places are limited to 15 people per tour, advance booking is essential. The tour lasts around one hour and is open only to visitors aged 12 and over.
A fortification has stood on the site at Birr since around 1170. It would nevertheless be inaccurate to describe the present castle as an intact 12th-century building: its architecture is the result of numerous phases of construction and alteration.
From the Middle Ages onwards, the fortress came under the control of the powerful O’Carroll clan. They ruled a territory in the Midlands known as Ely O’Carroll. The name therefore referred to the land controlled by the family, rather than paying tribute to one of its members.
In the 1580s, the property was sold to the Butler family of Ormond. In 1620, the fortress, then largely in ruins, was granted by King James I to Sir Laurence Parsons.
Rather than rebuilding the former O’Carroll tower, which has since disappeared, Laurence Parsons converted the Norman gatehouse into a residence. He added side wings and two flanking towers, creating the structure around which the present castle gradually developed.
After Sir Laurence Parsons died in 1628, the estate passed to his descendants. In 1641, at the outset of the Irish Rebellion and the Confederate Wars, William Parsons found himself besieged in the castle by Catholic forces.
The garrison held out for around fifteen months. Birr Castle endured a second siege during the 17th century, leaving the family in financial difficulty. These events explain why relatively little work was undertaken at the castle during the following century.
In the late 18th and early 19th centuries, the main façade was completely redesigned in neo-Gothic style. Once facing the town, the house now opened out towards the park. An octagonal Gothic drawing room overlooking the river was added around 1820.
A fire destroyed part of the central building in 1836. During its reconstruction, the ceilings were raised, a third floor was added and a large dining room was created. The last major works date from the 1860s, when a square tower was built on the eastern side.
Birr Castle owes much of its international renown to William Parsons, third Earl of Rosse. An astronomer, engineer and President of the Royal Society, he designed a reflecting telescope of unprecedented dimensions in the 1840s.
Completed in 1845, the Leviathan of Parsonstown had a metal mirror measuring 1.83 metres in diameter and weighing more than four tonnes. Its tube was suspended between two imposing masonry walls, allowing the instrument to be aimed at the sky.
The Leviathan remained the world’s largest telescope until the Hooker telescope at Mount Wilson Observatory in California entered service in 1917. Thanks to its power, William Parsons and his assistants were among the first astronomers to make out the spiral structure of certain nebulae, now identified as galaxies.
After scientific activity at Birr slowed in the early 20th century, one of the original mirrors was transferred to London’s Science Museum. The structure that remained at Birr gradually deteriorated before undergoing major reconstruction in the late 1990s.
The telescope visible today is a working reconstruction installed in its historic setting. Visitors can approach the instrument, take in its impressive structure and learn about the techniques used to make its mirrors in the 19th century.
The Birr Castle estate includes around 10 kilometres of paths through gardens and woodland, alongside two rivers, a lake and a waterfall. More than 5,000 species of plants and trees are recorded here, including magnolias, redwoods, maples and many specimens from Asia.
The gardens are divided into several areas with very different atmospheres:
A suspension bridge built around 1820 can also be seen from the estate. Although it has been restored, it is generally closed to visitors for safety reasons and opens only occasionally under supervision.
Families will find a large playground with climbing equipment, slides and what the estate describes as Ireland’s tallest treehouse. The ticket also allows access to St Brendan’s Well, an ancient pilgrimage site believed to date back to the 6th century.
Housed in the estate’s former outbuildings, Ireland’s Historic Science Centre traces the discoveries and inventions to which several generations of the Parsons family contributed.
Its seven galleries display astronomical instruments, photographic equipment, electrical apparatus and objects used in the construction of the Leviathan. Visitors can also discover the work of Mary Rosse, third Countess of Rosse and a pioneer of photography in Ireland. The estate notably preserves one of the oldest surviving photographic darkrooms.
Part of the exhibition is devoted to Charles Algernon Parsons, inventor of the modern steam turbine, while another area explains how I-LOFAR works, the radio telescope currently operated at Birr as part of a European scientific network.
Since 2025, Birr Observatory has appeared alongside Dunsink Observatory on Ireland’s UNESCO World Heritage Tentative List. This listing is a first step towards possible international recognition, but Birr Castle is not yet a World Heritage Site.
Address: Birr Castle Demesne, Rosse Row, Birr, County Offaly, R42 V027, Ireland.
GPS coordinates for the visitor entrance: 53.096704, -7.914320.
The estate does not have on-site visitor parking. Paid public parking is available at Marian Hall, directly opposite the main entrance. As the parking meter may require coins, it is best to bring some with you.
Most of the main paths are suitable for wheelchairs and mobility scooters, although some areas have slopes and steps. A lift provides access to the upper floor of the science centre. The castle interior tour, however, involves numerous stairs and is not wheelchair accessible.
Allow around two to three hours to explore the gardens, see the Leviathan and visit the science centre. Half a day is preferable if you add the guided castle tour or are travelling with children.
Picnics are permitted in designated areas. Dogs are welcome on the estate provided they are kept on a lead, but they are not allowed in the science centre, playground or castle.
After your visit, take time to explore the historic centre of Birr, known for its Georgian architecture. The castle can also be included in a tour of County Offaly, with a stop at the famous monastery of Clonmacnoise or in the natural landscapes surrounding Tullamore.
Sources: Birr Castle Demesne, The Great Telescope, Royal Society, Science Museum Group and UNESCO. Information checked on 25 August 2026.
Want to extend your visit without having to rush around? Here are a few well-located places to stay near the must-see attractions.
Essential information to help you plan your visit, including key landmarks, access information, and booking options.
53.096714, -7.914341
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The estate is open 362 days a year. In winter, it closes earlier due to reduced daylight, generally at around 4 pm.
For a guided castle tour, visitors are asked to report to reception 30 minutes before their booked time. No regular tours are held on Sundays during the 2026 season.
Birr Castle Demesne may exceptionally close in the event of high winds or dangerous weather conditions. Check the official Birr Castle opening hours before travelling.
Check the opening hours and admission requirements before you leave, especially during peak season or on Irish public holidays.
The general admission ticket includes access to the gardens and park, the Leviathan of Parsonstown, walking trails, Ireland’s Historic Science Centre, the playground and treehouse. It does not include an interior tour of the castle.
The guided castle tour is reserved for visitors aged 12 and over. It includes general admission to the estate. As tours are limited to 15 visitors, online booking is essential.
Check the official Birr Castle ticket office before your visit.
