You are not afraid of heights, right? Fantastic, because the ride up to the center of the dome in the glass elevator is well worth it. The Monument to the Revolution was to be the Congress, but only the dome was completed of the original project. You can walk by the view point at the top, between the two overlapping cupolas and even take a tour to the lantern itself. Take the camera; the clean lines of the architecture are stunning and the views over the city, spectacular both day and night, with the fountains and the building alight with color. 

On the ground floor, in a very industrial style, you have an interesting museum and you can stroll through the building foundations where famous public figures such as Madero and Villa are buried. Have a nice coffee in the cafeteria, or stroll among the fountains.