A little history

This is the Casa de Montejo located on the northern side of the zocalo. All that remains of the original construction is the façade. It was built in 1540 by the son of the first Montejo, who was defeated in his initial conquest of the Mayan.
The sign on the front of the building says it is the best example of Plateresque architecture in Mexico. It also says that it “ displays iconographic elements allusive to the Spaniard’s conquest and domination over the Mayans, as well as references to the Montejo family, It features the sculptures of two Spanish soldiers of the 16th century, standing on individual heads with expressions of pain and terror, as well as other figures located underneath, armed with mallets. As recently as the 1980’s this house was inhabited by descendants of the Montejo family.”
Imagine walking out on that balcony to address the assembled masses. Standing on a pile of tortured heads makes quite a statement.

And this is the auditorium in the Casa del Pueblo

quite a striking setting with the columns and PRI curtain.

If you look, you can see the name of the progressive politician and women's and indigenous rights advocate, Felipe Carrillo Puerto, above the stage and he has a statue in front of the building as well. A note of interest, the pre-PRI had Puerto assassinated in 1924.

You can read of his tragic love story here.

Look at the figures at the base. Those are his Mayan supporters holding him up.