A vertiginous bird's-eye view captures a lone bus negotiating the dramatic switchbacks of Cuesta de Mamulique, the legendary mountain pass on the Carretera Nacional linking Mexico City to Laredo — a road that opened Mexico to modern tourism and commerce in the late 1930s. Photographer A.M. Lopez framed the scene masterfully: the hairpin curve at center draws the eye down into a dense brushy canyon while the road reappears high on the opposite ridge, illustrating just how audacious this engineering feat was. The silver-gelatin real-photo surface gives the image exceptional tonal depth, with the Sierra Madre peaks dissolving into a pale sky behind. For travelers of the era, this pass was both thrilling and terrifying — the stuff of postcards sent home as proof of survival.