Arguably, the planet doesn't have a heart. But it certainly has a circulatory system. Birds migrate, magnetic fields pulse, ocean currents flow. And travelers—well, they travel, every year, on adventure-filled tracks. These are the circuits.

As routes, they are organic. They result from the collective calculus of a thousand dog-eared guidebooks; millions of miles by bus, burro, and flip-flop; and a lifetime of travelers' tales collected in guest houses and on bar stools from Darwin to Delhi to the Darién.

Like rivers and people, the circuits change every year. On the following pages, we've assembled the world's best. Consider them a snapshot, however fleeting, of the planet's circulatory system, 2003.

First Stop: Africa >>