BNKR Arquitectura wants to build a pyramid that penetrates nearly 1000 feet into the earth below Mexico City's largest and most historic public square. Its upper floors will be illuminated through a glass ceiling that will replace the paving stones of the current square, and its deepest reaches will receive daylight piped in from fiber-optic cables routed to the surface.
It's called an "earthscraper," and it's a unique solution to a problem affecting almost every large, historical city on earth. You can't build skyscrapers on what little undeveloped land is left in Mexico City, on account of height restrictions. Historical preservation, height restrictions, and density: Pick two. You can’t have them all. Unless you dig.
Critics charge that an earthscraper in Mexico City is madness given the area’s history of earthquakes, but of course seismic activity doesn't mean you can't build large structures; they just have to be built better. Hence this earthscraper's ultra-strong pyramid shape.
So far the mayor has refused to see the architects behind this design, so don't hold your breath on it becoming reality. Regardless, it's a solution that seems like it could work somewhere (something similar has been proposed in Arizona). After all, the world is already filled with famous underground buildings — including Apple's flagship store in NYC.
In Mexico City, an underground solution for sprawl, SmartPlanet.