Here’s what you’ll learn when you read this story:

• The legend of La Zona del Silencio surrounds a region in the remote Chihuahuan desert where, reportedly, radio signals mysteriously die due to unusually high deposits of magnetite.
• Although these claims have never been fully verified, the region has become a UFO hotspot, especially after a U.S. Athena rocket crashed in the region in July of 1970.
• While the Zone of Silence’s extraterrestrial credentials are spotty at best, the area is a natural desert wonder and home to amazing endemic species, including the Bolson tortoise—the largest land reptile in North America.

On July 11, 1970, a five-story, seven-ton Athena rocket raced toward the sky from a U.S. Air Force Base in Green River, Utah. Its mission wasn’t a military one—rather, it was a scientific endeavor to study the upper atmosphere. But something went terribly wrong.

Instead of returning to Earth near White Sands, New Mexico—the famous testing site of the first atom bomb in 1945—the rocket veered dangerously off course and crashed in the Chihuahuan desert in northern Mexico, leaving behind a trench 50 feet long, 17 feet wide, and 10 feet deep, according to a report weeks later by The New York Times.

While this stretch of desert might look like any other to most people, the rocket had actually inadvertently crashed-landed into a local legend: La Zona del Silencio, or the Zone of Silence. The true nature of the Zone of Silence is widely debated, but the story goes that this area—located in the Bolsón de Mapimí that mostly overlaps the Mexican states of Chihuahua, Coahuila, and Durango—contains unusually high levels of magnetite. Likely deposited into the dusty surroundings by frequent meteorite impacts, this magnetite allegedly interferes with radio signals and other electronic equipment. Of course, Mexico’s most famous impact occurred some 66 million years ago off the coast of the Yucatán Peninsula, but as Atlas Obscura reports, the Zone of Silence has received a few rocky, extraterrestrial visitors of its own over the course of the 20th century.

Magnetite, a naturally magnetic iron ore, can interfere with radio signals if concentrated in great enough quantities. And the Zone’s nickname—coined by an oil company executive in 1966 who couldn’t receive any radio signals in the area—does speak to this anomaly. But the jury is still out if there really is a naturally-occurring interference in the area, or if the cause is a bit more mundane: the area is just really remote.

However, a U.S. rocket crash, a remote desert, and strange local legends provided the perfect melange of intrigue to propel La Zona del Silencio into an international UFO sensation.

“There are lots of stories of aliens and unidentified flying objects in the Zone,” UFO investigator Geraldo Rivera told Atlas Obscura in 2016. “People often get lost in the Zone.”

Today, UFO and alien enthusiasts will venture into the remote region in search of their own extraterrestrial encounters, and the locals refer to them as “silencios” or “zoneros.” Unfortunately, however, some of these visitors take historical or natural artifacts with them, which doesn’t thrill those who work at the nearby Mapimí Biosphere Reserve—a group (established only a few years after that fateful missile mishap) that protects the Bolsón de Mapimí by restoring grasslands and soils while monitoring endangered species.

So, while tourists may look to the skies for evidence of the extraterrestrial, the true wonders of the Zone of Silence might be very terrestrial, especially if you’re lucky enough to spot the Bolson tortoise (Gopherus flavomarginatus)—the largest land reptile in North America. If you ever find yourself traipsing out into the Chihuahuan desert for an otherworldly experience, at the very least, please tread lightly.