Surprisingly, Mexico City is one of Mexico's best-kept secrets. Travelers often flock to the country's famous coasts, but neglect the cities of its colorful interior. Perhaps they are intimidated by the size of the capital—it's one of the largest, most densely populated metropolises in the world—or by rumors that it is chaotic, dirty, and dangerous. Yet intrepid visitors tend to return home enamored with “CDMX,” formerly known as the Distrito Federal. As journalist David Lida asserts: "Mexico City is the capital of the 21st century." After your first trip to this city, you'll see why it's only a matter of time before others discover the secret, too.