La Subterranea takes its name from a tunnel and viaduct system running underneath and through the city of Guanajuato, Mexico. As riverbed, vehicular thoroughfare, and the historical back-alley to the city, La Subterranea has evolved in a state of tension with the city above. Its use, form, and geography has shifted over time, registering changing attitudes towards hygiene, shifts in transportation and hydrological infrastructure, and alterations to the natural topography. While Guanajuato and La Subterranea co-evolved into the interwoven system it is today, their contingent development has produced spaces of uncertain allegiance--neither wholly of the subterranean nor wholly of the city proper. The result is an uneven morphology, a subtle incongruity of form and fabric--where an overlay of the two systems displays correspondences of alignment and access and at times a counter patterning of seemingly mis-registered street axes. In this interference pattern lies the fundamental ambiguity of this system, where La Subterranea reads simultaneously as artifact and void.