What is the zone of silence in Mexico?

Answer 1

27 °N is such parallel. Oddly enough, it is the same parallel that touches other singular places and anomalies around the world like the Bermuda Triangle, the Canary Islands, the Pyramids of Egypt, and the Himalayas.

Answer 2

It is a 1600 sq km (618 sq mi) area in northern Mexico, located at the intersection of the states of Chihuahua, Coahuila and Durango. Its coordinates are (26.691389°, -103.745556°), and nowadays it belongs to the Mapimi Biosphere Reserve.

In the 1970's a missile with a couple of radioactive containers filled with Cobalt-57 was launched from the United States' White Sands Missile Range and lost its guidance, falling within the region. Search took three weeks, and several train containers were filled with contaminated soil and several biological specimens. A few years after the event, some locals began to circulate the urban legend that radio waves including AM, FM and short wave cannot function; on the contrary, from time to time radio-waves from places as far as Tokyo or Shanghai can be heard. Hence, the "zone of silence". Then, increasingly exotic urban legends began to circulate, such as strange light phenomena during the night, mutated animals, extraterrestrials and star portals.

Nowadays, the region has been plundered by fossil seekers, paranormal believers and endangered species traffickers. There are a couple of desert research stations, where no strange electromagnetic phenomena has been reported. This evidence however, is still ignored by conspiracy theorists who believe the region holds an underground extraterrestrial base, or a lost Mayan city.