Its impact is heightened by the drama of its setting high on a hill, which makes the approach, along narrow woodland paths, feel appropriately enough like a passage from one world to another. Within the complex, the courtyards function as great rooms open to the sky, while the buildings are layered, permeable, the boundaries between inside and outside, light and dark, blurred and ever-changing. Finest, intricately-carved marble and wood is contrasted with basic stucco.

The two great courtyards - the Court of the Myrtles with its long pool and the Court of the Lions with its fountain supported on twelve of the marble beasts - are of very different characters, one public, one more intimate, though each plays subtle games with notions of symmetry and axis. Inside, the marvel is the virtuosity of the carved decoration, especially in the Hall of the Two Sisters where it bursts into a prismatic explosion like a cave of crystalline stalactites. Awed silence is the only proper reaction.

Happily the merits of the Alhambra were recognised as early as 1828, when what became a permanent restoration began. Its abstract geometrical decoration had a huge impact on British decorative arts later in the century, it influenced the decoration of the Crystal Palace of 1851, and its name eventually became a byword for any form of pleasure palace, from music halls to cinemas. But the Alhambra was never a place of frivolity. It was built in troubled times to command a kingdom. The Moorish soldier-kings, however, hankered after more than that. They built their fortress as a retreat of sublime tranquillity.