Which ancient wonder stood at Alexandria?

The Lighthouse, the Pharos, built around 280 BC and something like 100 metres tall - among the tallest structures in the world for most of the following 1,600 years. A fire burned at the top at night and a polished metal mirror reflected sunlight by day, reportedly visible for tens of kilometres.

It was the longest-surviving of the ancient wonders except the pyramids, and it went slowly rather than dramatically - a series of earthquakes between the tenth and fourteenth centuries brought it down in stages, and the stone was eventually used to build a fort on the same spot, which is still there. Divers found large blocks and statuary on the harbour floor in the 1990s.

Its name became the word. Pharos gives us phare in French, faro in Spanish and Italian, and pharology as the study of lighthouses - a building so definitive that its name replaced the generic term across half of Europe. The city's other wonder, the Library, has a mythology of its own that outruns the evidence: there was no single catastrophic burning, and the more likely story is centuries of underfunding, neglect and the gradual loss of the scholars who made it matter.