Once your eyes get used to Mexico City's smoky ensemble and your ears to the staggering density of 5,950/sq km, you'll see in this packed ball of people a bright palette of intriguing contrasts, and hear an exquisite musical performance in the effervescence of street life. When you stand in the middle of Zocalo, imagine that it's been the heart of activity since the Aztec times. When your jaw drops on seeing the Santa Fe financial district, realize there are hundreds of cardboard "houses" erected in the suburbs. When it's almost dawning and bar stools are still wobbling, recall the genuine piety you've seen at the Basilica of Our Lady of Guadalupe, and try to remember the impression you get when, having just left the Palace of Fine Arts, you stumble upon a street mime accompanied by an enthusiastic crowd. Hazardous but exceptionally welcoming. Sophisticated like Museo Nacional de Antropología but at the same time natural and unrestrained like Frida Kahlo. It's a rare thing to be at both the center of history and a hub of all that epitomizes the modern world.