The revolutionary home of Lord Armstrong, Victorian inventor and landscape genius, was a wonder of its age. Built on a rocky crag high above the Debdon Burn, Cragside is crammed with ingenious gadgets and was the first house in the world lit by hydroelectricity. Even the variety and scale of Cargside's gardens are incredible. Surrounding the house on all sides is one of the largest "hand-made" rock gardens in Europe. In the Pinetum below, England's...