Scouring other resources, in a city this large it is indeed possible to find places of interest off of the usual grid. At the end of one of the northern metro lines, and then just across the border into Mexico State (this does get confusing: there is Mexico the country, Mexico City, and Mexico State, and when people talk about Mexico here, for historical reasons they tend to mean the city, because this was Mexico before the others were Mexico) there is a set of ruins from or related to the Chicimeca culture, which the Aztecas conquered and assimilated. Their capital was Tenayuca, and its main pyramid was copied and enlarged to create the Templo Major, the greatest Aztec pyramid. There are now two archaeological sites for the former city. The first is the main pyramid, partially reconstructed and open for climbing. The base on three sides is flanked with a row of snake sculptures of various sizes, and the walls of the pyramid are adorned with more carved snake heads. The remaining west side, with the staircase (so placed to watch the sun 'hide' each day) has, in front of it, an Adosada platform as seen at Teotiuhacan and elsewhere. Being a Sunday, however, the aim of avoiding people was not entirely met, and what is more, being the first day of spring, many more folk than usual where on the top, arms stretched out to absorb cosmic spirit rays, and lining up on the platform to receive some blessing which looked more like a shaking by the shoulders followed by a forehead slap. Pavel, who traveled with me, decided to absorb cosmic healing aura into his hemorrhoids (real or imagined) and assumed the position. This maybe did not win him friends.
Thus, we moved slightly further north to the related pyramid of Santa Cecilia Acatitlan. As with all pyramid cities they found, the Spaniards removed the external structures of the site to build a church. In the 1960s the last remaining pyramid, adjacent to the church, was restored, with its crowning temple rebuilt. This site had fewer people, but enough to clutter up photos. Still, it was a very pleasant place, and being more complete than other pyramids, more evocative.
Update: galleries are working again.