ISTANBUL Istanbul is a grand Turkish metropolis that extends across two continents and is influenced by various cultural and historic epochs. In the bright and ornate interior of the Hagia Sophia the splendid yet contrasting influence of both Christian Byzantine and Ottoman architecture has been preserved to the present day. Beneath the second largest cupola in the world, each of these cultures and religions unite in perfect harmony. Not far from the Hagia Sophia is the Yerebatan Saray that provides a fascinating insight into Constantinople's former water supply. Three hundred and thirty six columns support the vaulted ceiling of the cistern that was built in around 532 A.D. The Topkapi Palace was built by Sultan Mehmet The Second. It is one of the city's main tourist attractions and its exquisite interior indicates the lifestyle of the city's former Ottoman rulers. As the capital of three former World Empires, Istanbul truly enjoys a unique position among the great cities of both Europe and Asia. Global Treasures - History's Most Protected Monuments - Heritage is our legacy from the past, what we live today, and what we pass on to future generations. our cultural and natural heritage are both irreplaceable sources of life and inspiration. Places as unique and diverse as the wilds of East Africa's Serengeti, the Pyramids of Egypt, the Great Barrier Reef in Australia and the Baroque cathedrals of Latin America make up our world's heritage. Join us as we explore one of these protected monuments.