Lying to the west of Emmet Square, Birr's forbidding Gothic castle itself is not open to the public, but there’s plenty of interest in the Historic Science Centre in the coach houses, which also shelter a pleasant summertime café, and in the varied grounds. In the nineteenth century, the Parsons family gained an international reputation as scientists and inventors, partly it would seem because they were educated at home. The third Earl of Rosse, William Parsons, devoted himself to astronomy, and in 1845 built the huge Rosse Telescope, with a 72-inch reflector, which remained the largest in the world until 1917. It was fully reconstructed in the 1990s, along with the massive, elaborate housing of walls, tracks, pulleys and counterweights needed to manoeuvre it, which can be seen in the garden. The fourth Earl, Laurence, and his mother, Mary, a friend of Fox Talbot’s, were eminent photographers, while Laurence’s brother, Sir Charles Parsons, was carving himself a varied and colourful career, which included building a small flying machine and a helicopter in the 1890s and spending 25 years unsuccessfully trying to make artificial diamonds. He’ll be best remembered, however, as the inventor of the steam turbine and for his exploits at the 1897 Spithead Naval Review, celebrating Queen Victoria’s Diamond Jubilee when, frustrated at the Royal Navy’s foot-dragging, he gatecrashed in the Turbinia, the first steam-turbine ship, racing through the fleet at the unheard-of speed of 34 knots. Within a few years the technology was adopted by navies and passenger liners around the world. All of this is set in historical and global context in the Science Centre, with plenty of astrolabes, cameras and other instruments and some lively audiovisuals.
You could easily spend a couple of hours strolling around the beautiful castle grounds (demesne), especially if you buy the booklet on its fifty most significant trees. Beyond the wild-flower meadows, which are left to grow tall until July every year, lie a nineteenth-century lake, a fernery and fountain, and the oldest wrought-iron suspension bridge in Ireland, dating from 1820. The walled gardens feature the tallest box hedges in the world, which are over three hundred years old, as well as intricate parterres and paths canopied with hornbeams in the formal, seventeenth-century-style Millennium Garden.