This magnificent neoclassical mansion stands at the northern end of Hampstead Heath in a glorious sweep of landscaped gardens that lead down to a picturesque lake. The 17th-century house was substantially remodelled in the 1760s and rescued from developers by Edward Cecil Guinness, 1st Earl of Iveagh, who donated it and the wonderful collection of art it contains to the nation in 1927. Among its treasures are paintings by Rembrandt (one of his many self-portraits), Constable, Gainsborough and Vermeer.
The Iveagh Bequest, as it is known, is one of the finest small collections in Britain. Head up the great stairs for the Suffolk Collection, consisting of Jacobean portraits by William Larkin and a set of royal Stuart portraits.
The house was extensively refurbished in 2013, with rooms repainted in their original 18th-century colours. The Great Library, with its powder-pink and sky-blue vaulted ceiling and vignette paintings, is magnificent.
The gardens are another highlight; you'll find sculptures by Henry Moore and Barbara Hepworth on the lawn. The old servants' wing now houses a sit-down cafe and a snack bar with an ice-cream counter.