The old walled city of Istanbul stands on a triangular peninsula between Europe and Asia. Sometimes as a bridge, sometimes as a barrier, Istanbul for more than 2,500 years has stood between conflicting surges of religion, culture, and imperial power. For most of those years it was one of the most coveted cities in the world.

The old city contains about 9 square miles (23 square km), but the present municipal boundaries stretch a great deal beyond. The original peninsular city has seven hills, requisite for Constantine’s “New Rome.” Six are crests of a long ridge above the Golden Horn; the other is a solitary eminence in the southwest corner. Around their slopes are ranged many of the mosques and other historic landmarks that were collectively designated a UNESCO World Heritage site in 1985.