Once known as Constantinople and Byzantium, Istanbul's position on the Silk Road has made it an economical, historical and cultural center, serving as an imperial capital multiple times for the Roman, Byzantine, and Ottoman empires. With both Asian and European sides to the city, there's a lot to explore. The old walled neighborhood of Sultanahmet is home to some of the most recognizable sights, such as the Hagia Sophia, with its dazzling mosaics and the enormous dome that has covered this space since the sixth century, when it was a Roman basilica. You'll also want to experience Topkapi Palace—containing lavish interiors and many Christian and Islamic relics—as well as the Blue Mosque and the giant underground Basilica Cistern. City views of the river suggest the next step: A Bosphorous cruise, navigating along the vast expanse of water that unites two continents, provides a wonderful way to see the banks of the Golden Horn. To delve into the local culture, as well as for help with haggling, visitors can take a private tour of the Grand Bazaar and the Spice Bazaar, containing some of the richest smells in the world. For longer visits, tours from Istanbul can take visitors far and wide to the remarkable rocky landscapes of Cappadocia, the ruins of the Greco-Roman city of Ephesus, and even to the WWI sites of the Gallipoli Peninsula.