İstanbul, Turkey

Straddling Europe and Asia, the curriculum vitae of İstanbul includes stints as capital of the Byzantine and Ottoman Empires. It's quite simply one of the world's greatest cities. The historical highlights cluster in Sultanahmet – the Aya Sofya, Blue Mosque, Topkapı Palace and Grand Bazaar. After marvelling at their ancient domes and glittering interiors, it's time to experience this 13-million-strong metropolis's vibrant contemporary life. Cross the Galata Bridge, passing ferries and fish-kebap stands, to Beyoğlu, a nightlife hot spot full of chic rooftop bars and rowdy taverns.