The citadel of Saladin - and indeed, the Cairo skyline - is dominated by the Alabaster Mosque, or Mosque of Mohammed Ali. Modelled along classic Turkish lines, it took 18 years to build (1830 - 1848) although later the domes had to be rebuilt. It was commissioned by Mohammad Ali, ruler of Egypt from 1805 - 1849, who lies in the marble tomb on the right as you enter.
Perhaps the most evocative description of it is in Olivia Manning's The Levant Trilogy: "Above them Mohammed Ali's alabaster mosque, uniquely white in this sand-coloured city, sat with minarets pricked, like a fat, white, watchful cat." It has never found much favor with writers, who have criticized it for being unimaginative, lacking in grace and resembling a great toad. Note the chintzy clock in the central courtyard, a gift from King Louis-Philippe of France in thanks for the Pharaonic obelisk that adorns the Place de la Concorde in Paris. It was damaged on delivery and has yet to be repaired.
The easiest way to travel around Cairo is by organized tour or private car and guide. If you choose a private car, just be firm that you do not want to visit all the perfume and carpet shops!
