Guarding a picturesque bend of the River Eske, Donegal Castle remains an imperious monument to both Irish and English might. Dating to the 15th century, the castle was rebuilt in 1623 by Sir Basil Brooke, along with the adjacent three-storey Jacobean house. Further restoration in the 1990s has made it an atmospheric place to visit; rooms are furnished with French tapestries and Persian rugs. There are guided tours every hour.
Built by the O'Donnells in 1474, it served as the seat of their formidable power until 1607, when the English decided to rid themselves of pesky Irish chieftains once and for all. Rory O'Donnell was no pushover, though, torching his own castle before fleeing to France in the infamous Flight of the Earls. Their defeat paved the way for the Plantation of Ulster by thousands of newly arrived Scots and English Protestants, sowing the seeds of the divisions that still afflict Ireland to this day.