This magnificent 90-room, 17th-century castle stands amid gorgeous, sprawling gardens, beautifully crafted as a kind of wonderland. The great house is still lived in by the same family that has owned it for centuries. It is only open to the public from May to August, 6 days a week—and even then for just a handful of pricey guided tours, limited to 15 adults, so advance booking is essential. But the real reason to come to Birr is to see the extraordinary grounds, which are open year-round. The demesne (estate) of the Parsons family, now the earls of Rosse, wraps around a peaceful lake and stretches over miles of pastures and wild woodland. There’s much to discover—beautiful topiaries, huge box hedges, a lovely wrought-iron bridge, a newly renovated science exhibition, and even a steampunk-esque, 19th-century telescope. There’s also a charming tea shop and a play area for kids.