Ventilation tubes and electricity cables run along the rough-hewed walls. Rudimentary rails stretch along the ground. The dank, waterlogged conditions belie the desert conditions at the surface, some 70 feet above.

Pictures and video of the remarkable smuggling tunnel, the longest ever found at the Mexico-United States border, were released by the American authorities on Wednesday. The shaft stretched some 4,309 feet, nearly a mile, between Tijuana, Mexico, and the outskirts of San Diego.

“The sophistication and length of this particular tunnel demonstrates the time-consuming efforts transnational criminal organizations will undertake to facilitate cross-border smuggling,” Cardell T. Morant, the acting special agent in charge of Homeland Security Investigations in San Diego, said in a statement from United States Customs and Border Protection.