Glenveagh (Gleann Bheatha, "glen of life", in Irish) — covering 110 square kilometres of hillside above Glenveagh Castle on the shore of Lough Veagh (Loch Ghleann Bheatha), some 20 km from Gweedore in County Donegal, Ireland — forms the heart of the Glenveagh National Park (Páirc Naisiúnta Gleann Bheatha), the largest in Ireland. The network of mainly informal gardens displays a multitude of exotic and delicate plants from as far afield as Chile, Madeira and Tasmania, all sheltered by windbreaks of pine trees and ornamental rhododendrons.
The gardens and castle were presented to the Irish nation in 1981 by Henry P. McIlhenny of Philadelphia who had purchased the estate in 1937. The park now has the largest herd of red deer in Ireland and golden eagle, formerly extinct in Ireland, were reintroduced into the park in 2000.
Glenveagh Castle (Irish: Caisleán Ghleann Bheatha ) is a large castellated Mansion house built in the Scottish Baronial style, situated within Glenveagh National Park near Churchill and Gweedore, County Donegal, Ireland. The castle was built between 1870 and 1873 and consists of a four storey rectangular keep surrounded by a garden, and has a backdrop of some 165.4 km² (40,873 acres) of mountains, lakes, glens and woods complete with a herd of red deer. The Visitor Centre has displays that explain the park as well as an audio-visual show and is accessible for visitors with disabilities. The gardens and castle were left to the Irish nation in 1981 by Henry Plumer McIlhenny of Philadelphia, who had purchased the estate in 1937. Hollywood stars such as Marilyn Monroe and Greta Garbo stayed at the castle while McIlhenny owned it. The Irish Gleann Bheatha translates into English as "Valley of the Birches".
The castle was built by Captain John George Adair (1823-1885), a native of Co Leix, and a member of the minor gentry. Adair had made his fortune by chancy land speculation in the United states, and he returned to Ireland and bought up vast tracts of land in Donegal. Adair had married in 1869, Cornelia Wadsworth Ritchie, a daughter of James S. Wadsworth, a Union General in the American Civil War. Together they set about the creation of the Gardens and Castle. Adair's ambition was to create an estate and castle that surpassed Balmoral, Queen Victoria's Scottish retreat. John Adair is remembered with scant affection in Donegal. On the heels of the Great Irish Famine and emigration on a par with the Highland Clearances, John Adair evicted 224 tenants from their black houses on his land. This was not for financial gain, but merely to improve the æsthetic aspect from the castle.