I've been to anthropology museum on a previous trip, so looking for the other must-sees. Frida khalo and Trotsky house? Tamayo museum? Mercado central?
With only one day, I'd take the hop-on hop-off bus wich will give you a overall idea of Mexico city. You can choose where to hop-off and spend more time, for instance, downtown is nice, including El Zocalo ( main square) and Palacio de Bellas Artes. Enjoy Mexico city (DF)! over 7 years ago