26.6917°N, 103.7458°W.
The Zona del Silencio (Mapimí Silent Zone) is a stretch of high desert in the Bolsón de Mapimí basin on the borders of Durango, Coahuila, and Chihuahua states in northern Mexico, popularly believed to absorb radio signals. The reputation dates principally to the July 1970 crash of a US Air Force Athena RTV launched from Green River, Utah, which carried two small cobalt-57 sources and impacted near the village of Ceballos; recovery teams and the resulting decade of US-Mexican cleanup activity drew sustained press attention to the area. Subsequent claims of routine radio dead zones have not been reproduced under controlled measurement, and modern cell and radio communication functions normally across the basin. The desert itself is genuine and biologically rich — the Mapimí Biosphere Reserve was established here in 1979 and protects the endangered Bolson tortoise.
The Zona del Silencio is famous for what it is supposed to do, not for anything it has been measured doing.