Mexico City: Huge but Invisible

I am in Mexico City, the biggest city on Earth by some measures, with more than 20 million inhabitants. Outside my hostel is a street market. This market seems to stretch indefinitely along the road. You can walk for 2 hours along the street and the market never ceases.

Yet the city is partly invisible. This is because the air is heavily polluted. The city lies on a high plateau surrounded by mountains and volcanoes that trap the emissions of the traffic of this mega-city, ensuring that the size of the city is obscured. The Mexicans claim that the mountains are there but I can't see them, only a cloudy, smoggy horizon.

I am staying two minutes walk from the "Zocalo" or main plaza, which is one of the largest city squares in the world. There is always something interesting and noisy going on in the Zocalo. There are people dressed in Aztec garb dancing in a circle to thumping drums. There are people protesting against various federal and regional governments. There are the ubiquitous Mexican street markets, tourists ogling the sights, students loitering, and once a day the flag changing ceremony. Passing through the Zocalo is always an adventure, dodging the traffic that runs around the outside of the Zocalo, refusing the pleas of the stall owners, and being confronted with legless beggars. There is Mexican music, Mexican smells, and Mexican sights.