Cairo is one of the world's great megacities — 20 million people, an ancient river, and 5,000 years of layered history. The Egyptian Museum houses the world's greatest collection of ancient artefacts including the complete treasures of Tutankhamun's tomb. The Pyramids of Giza and the Sphinx stand 30 minutes from the city centre at the edge of the Sahara. Islamic Cairo's Khan el-Khalili bazaar, the Al-Azhar Mosque, and the Coptic quarter add civilisational depth to an already overwhelming city.