Mexico city in two days. Here are the highlights:
To see: The pyramids of Teotihuacan, one of the largest cities of the world during the first millennium. Try climbing to the top and get a decent work out while you're at it.
To see: Museo Soumaya. Founded by Carlos Slim, Soumaya is the most visited art museum in Mexico comprising one of the biggest Rodin collections to date.
To explore: San Ángel. Go for the art galleries, artisan markets, and picturesque colonial feels for a nice Saturday afternoon before the September rain.