Alhambra

In 1812, Napoleon's army was leaving Granada, and before it left it packed the towers of the Alhambra with explosives. Several went up. The story told ever since is that a crippled Spanish soldier left behind in the fortress crept along the walls and cut the fuses before the rest could blow. Nobody can say how much of that is true. What is certain is that the towers that still stand were very nearly rubble, and that the palace which survived was in such a state that, seventeen years later, an American writer could rent rooms in it for next to nothing.

That writer was Washington Irving. He lived in the Alhambra for a few months in 1829, among the squatters, goats and dry fountains that occupied it, and turned what he heard there into "Tales of the Alhambra". The book was a European sensation. Most of the people walking through the courtyards today are, in a roundabout way, following him in.

The name means "the red one" in Arabic, after the colour of the hill's soil and the rammed-earth walls. There was a fortress here by the ninth century, but the Alhambra as we know it begins in 1238, when Muhammad ibn al-Ahmar set up a small emirate in Granada as Christian Castile closed in from the north. His Nasrid dynasty ruled from this hill for two and a half centuries, the last Muslim state on the Iberian peninsula, surviving much of that time by paying tribute to Castile. The most delicate rooms in the palace were built by rulers who knew precisely how precarious their position was.

It is not one palace but a walled town: the military Alcazaba at the western tip, the royal palaces in the middle, a quarter for craftsmen and servants beyond them, and the Generalife, a summer retreat, on the slope above. What made any of it possible was water. A channel roughly six kilometres long drew from the River Darro and carried it up to the ridge, where it fed pools, fountains and narrow runnels cut through the floors of the rooms themselves. On a dry hill above a hot city, the sound of running water everywhere was the real display of power.

The rooms people queue for are fourteenth-century. The Comares Palace belongs to Yusuf I, the Palace of the Lions to his son Muhammad V. The fountain in the Court of the Lions rests on twelve marble lions, and the verse carved around its basin, by the court poet Ibn Zamrak, has the water speak for itself. The ceiling of the Hall of the Two Sisters is built from thousands of tiny plaster cells stacked like a honeycomb, and from below you cannot find its edges. Every wall is written on: Quranic verses, poems, and the dynasty's motto, "There is no victor but God", repeated more times than anyone has counted.

Now the part that changes how you see it. All that stucco is cream and white today, but it was painted. Traces of red, blue and gold pigment survive in the carving. The Alhambra the sultans knew was far louder than the pale, elegant place in the photographs.

In the first days of 1492 the last emir, Boabdil, handed the keys to Isabella of Castile and Ferdinand of Aragon. The palace became Christian royal property and the alterations began at once. In 1527 their grandson Charles V started a vast Renaissance palace with a circular courtyard right against the Nasrid rooms; it was never finished and stood roofless for centuries. The mosque came down and a church went up. Then the court lost interest, and the Alhambra became a garrison, a prison and a storehouse. An earthquake in 1821 shook what the French had left.

The nineteenth-century rescuers did their own damage. The Contreras family of restorers, working for decades after 1847, added details they felt looked suitably Moorish, including an oriental dome on one of the pavilions in the Court of the Lions. In the 1920s Leopoldo Torres Balbás stripped out most of these inventions and put the restoration on a documentary footing. What you see is the result of a century of deciding which layers to keep.

One more oddity. The ceilings of the Hall of the Kings carry figurative paintings on leather: hunting scenes, knights, ten seated rulers. Figures this prominent in an Islamic palace are rare, and the painters may have been Christian. The twelve lions, meanwhile, were lifted out in 2002, cleaned one by one for a decade, and returned in 2012.

The Alhambra and Generalife are run by a public trust under the regional government of Andalusia and have been a UNESCO World Heritage Site since 1984. Around two and a half million people visit each year, and entry to the Nasrid palaces is capped daily; tickets often sell out weeks ahead. The quiet threat is not the crowds but what they bring with them. Moisture, heat and breath are slowly crumbling the plaster, and the fate of seven-hundred-year-old walls now depends on how many people stand in front of them each day.