Istanbul
Istanbul is often described as 'the crossroads of Europe and Asia' - a heaving bazaar-city of carpets and caravanserais with an imperial history stretching back for more than 1,500 years. This metropolis of an estimated 15 million occupies both sides of an east-west land bridge divided by the 32km (20-mile) Bosphorus Strait, which also connects the trade routes of the Black Sea to the Sea of Marmara and the Mediterranean. As a result, the city has been a jealously guarded centre of world trade since the Byzantine era, and protected by water on three sides, with the natural harbour of the Golden Horn nestled within the city.