Istanbul is a city built on layers of empire. Spanning two continents, it was once the capital of three major empires: Roman, Byzantine, and Ottoman. Visitors walking through the Sultanahmet district can witness this timeline firsthand, from the Roman-era Hippodrome to the Byzantine mosaics of Hagia Sophia, and the towering minarets of the Blue Mosque. At nearby Topkapi Palace, rooms still display the jeweled swords, ceremonial robes, and handwritten Qurans once used by Ottoman sultans.

A series of gates surrounds the two centers of ancient, medieval Fez (sometimes spelled Fes). The principal axes link the center to the gates and a street surrounds the heart of the old city. The Kairouan quarter, which is longer, is crossed by an artery. Narrow, tortuous pedestrian streets, covered passages, stairs and numerous dead-ends make up the dense layout with few urban squares.

Whitehorse, the capital of Canada’s Yukon Territory, sits along the Yukon River and serves as the cultural, economic, and transportation heart of the North. Its history is closely tied to the Klondike Gold Rush of the late 1890s, when prospectors passed through the area on their way to Dawson City.

Khiva, located in western Uzbekistan’s Khorezm region, is one of Central Asia’s most evocative Silk Road cities.

Khartoum, the capital of Sudan, sits where the Blue and White Nile rivers meet, creating a unique landscape of waterways, islands, and riverbanks.