Mexico City is one those places most people have a definite opinion about. They either love it or hate it. I've never heard anyone say 'yeah it was an OK trip'. When I was young my family would try to keep out of the city. My father would drive miles out of his way to avoid it. At the time we considered it dirty, polluted, crime infested, corrupt, and congested. The worst of Los Angles and New York City combined.
It is the capital of México and the seat of the federal powers of the Méxican Union. It's also the Federal District, which is a federal entity within the country that is not actually anyone of the 31 states but belongs to the federation as a whole. Think Washington DC in the United States. A place with problems but few ways to help itself.
Mexico City has so many places to visit museums, modern architecture, colonial architecture, ancient ruins, more than any other American city (North or South). It has extreme cases of poverty and wealth sometimes right next door to each other. It has some beautiful sights but as a whole it is not a beautiful city, it IS very alive with food people and traffic.
Sanborns (Casa de los Azulejos)
México City, later DF and now CDMX is huge and has been settled since 1325. Cortéz destroyed the indigenous city trying to erase all that was Aztec. Today the city has a population of over 9 million, the greater area about 22 million residents. The original city was built on a drained lake. Now the disappearing water table and soft clay soil is a planning engineers nightmare. Most the historical downtown is sinking. Stone structures built to last hundreds of years are sinking/leaning. Water and sewer lines laid years ago are bending, cracking and need constant maintenance.
The city is located at about 7400 feet in elevation this thin air in basin surrounded by mountains help trap in the air pollution. A smoking active volcano is always in the background. They have an occasional earthquake. The last big one was in 1985, it destroyed parts of the city and killed at least 5000. You do not visit México City to just get away from it all and relax.
México City is a very in your face experience. You can walk by a street performer, a bakery, a vendor grilling meats, clothing store and a broken sewer line all in the same block. So many places to visit in Mexico City. Travel with a pocket full of change, help out the college kid singing opera or the organ grinder with the fake monkey.
Palacio de Bella Artes
The City has 16 boroughs when you visit you might see two or three. Do not try and 'see it all'. Pick and choose, leave yourself plenty of time to get lost and sidetracked. Ubers are clean, plentiful and very cheap. You must see the Zocalo and surrounding buildings. Have lunch or drinks on a roof top restaurant and over look the plaza, it is huge. México City is the only city in the world that I bought a guide book. An excellent one is by Jim Johnston, Mexico City, an opinionated Guide for the Curious Traveler.