evidence: Another long day done. Our team of eight—three Americans, our Pakistani guide, and four Wakhi horsemen—is walking the Wakhan Corridor, Afghanistan's ancient, forgotten passageway to China. We are more than halfway through, en route to Tajikistan. Marco Polo passed this way 734 years ago. It was medieval then, and it still is. [...] In 2000, Greg Mortenson and I hatched the idea of traversing the length of the Wakhan Corridor, the thin, vestigial arm of northeastern Afghanistan that extends eastward to the border of China, separating Tajikistan from Pakistan. As founder and director of the Bozeman, Montana–based Central Asia Institute (CAI), a nongovernmental organization that has built more than 50 schools in the tribal borderlands of Pakistan and Afghanistan, Greg had plenty of experience navigating the region's dicey political landscape. [...] If any region of the country stands apart, it's the remote, sparsely populated Wakhan Corridor, which has been spared much of the recent bloodletting. Carved by the Wakhan and Panj rivers, the 200-mile-long valley, much of it above 10,000 feet, separates the Pamir mountains to the north from the Hindu Kush to the south. For centuries it has been a natural conduit between Central Asia and China, and one of the most forbidding sections of the Silk Road, the 4,000-mile trade route linking Europe to the Far East.