Stretching roughly 2,600 miles (4,184 kilometers) from Tibet to the East Sea, the sinuous Mekong is the thread that connects Indochina’s diverse cultures. It flows through six nations of China, Myanmar (Burma), Laos, Thailand, Cambodia, and Vietnam with more than 1,200, it has the third highest diversity of fish species in the world (only the Amazon and the Congo have more). For the past 800 years, explorers from Kublai Khan to Frenchman Francis Garnier have sought to conquer the river and the region that surrounds it, sending warrior hordes south toward Cambodia’s Angkor Wat or dispatching parties in dugout canoes north from Saigon (now Ho Chi Minh City). These early expeditions survived tigers, leeches, and quicksand, but never completely penetrated the Mekong Basin or reached the river’s source, in Tibet. An expedition cruise between Ho Chi Minh City and Siem Reap allows you to see more of the region in less time than on self-powered journeys. Pandaw Cruises runs two custom-built colonial-era teakwood steamers up and down the river. You’ll float past Cambodia’s capital, Phnom Penh, and go ashore to hike the country’s Wat Hanchai hill, home to ancient Champa shrines. Onboard, languorous hours are spent sipping gin-and-tonics on the deck as the jungle drifts by.