a city of doors, mostly closed

Massive gates opened into the city, and the winding streets themselves often ended abruptly at smaller doors that defined neighborhood and community boundaries... Whole neighborhoods might be walled off, accessible only by a single door in a narrow street. - Nina Burleigh

Over at BLDGBLOG, a great meditation on the nature of access, labyrinthine and boundary in 18th century Cairo as explored in Nina Burleigh's recent book Mirage. Sounds like an excellent read.