The fabled Chupacabra in Puerto Rico's El Yunque National Forest may be linked to UFO sightings in the area and a secret US government research facility.

Ghost sightings, a secret government time-travel experiment, and Native American battles suggest that Pennsylvania's Gettysburg National Military Park is a place of unusual and mysterious power.

A bizarre series of incidents in Big Bend National Park suggests that extraterrestrials are present in this remote wilderness area, leading experts to conclude that aliens have been secretly mining rare minerals there for years.

A series of disturbing deaths and disappearances, plus the unearthing of artifacts from an ancient race of people in Death Valley National Park leads to the discovery of malevolent forces that are believed to inhabit the park's secret underworld.

Terrifying encounters with gun-wielding ghosts and strange, savage creatures in Cleveland National Forest leads to the discovery of the area's bloody and tragic history and its link to the existence of portals into other dimensions.

An alien abduction and strange encounters with a humanoid monster in Apache-Sitgreaves National Forests point to a longtime extraterrestrial presence in the area. Are aliens using the forests to monitor nearby nuclear weapons facilities?

Mysterious lights, mechanical sounds from deep within the Earth and the disappearance of dozens of aircraft over the Great Smoky Mountains National Park could be evidence of a powerful secret society with an underground base in the area.

Mark Twain National Forest, haunted by hellhounds and other demonic creatures, may also conceal treasures from a lost civilization, pointing to the area's importance as a locus of dark, mysterious energies.

The ancient Anasazi built Chaco Canyon National Historical Park, but now the area is stalked by shape-shifting creatures and visited by time travelers who left behind a mysterious artifact. These and other bizarre encounters suggest the park may be a portal between our world and distant star system.

One of America's most beloved wilderness areas, Yosemite National Park, has a dark side. Experts believe the ghost and UFO sightings, mysterious disappearances and a prehistoric pterodactyl are caused by a rift in the fabric of time.

The shimmering waters of Crater Lake National Park captivate visitors, but they may also be the epicenter of dark, sinister forces from Native American lore that lure visitors to their deaths, conceal a terrifying monster and produce ghostly apparitions.

A demonic truck driver, disembodied voices, nightmarish skinwalkers and a time loop are among the bizarre phenomena found in Canyonlands National Park, where the mineral quartz may be acting as a recorder of human experience.

Black magic, mysterious deaths, and violent fireballs haunt Hawaii's Volcanoes National Park. Many believe this is the work of Pele, the fire goddess.

A Bigfoot-like creature and UFO sightings suggest that California's Joshua Tree National Park may be ground zero for alien genetic experiments.

A secret, underground Nazi base may be the reason for UFO sightings in Montana's Glacier National Park. It may also be the final hideout for Adolf Hitler himself.

A tragic plane crash, shocking murders, and mysterious python infestation suggest a dark, evil power at the heart of Florida's Everglades National Park.

Black magic, mysterious deaths, and violent fireballs haunt Hawaii's Volcanoes National Park. Many believe this is the work of Pele, the fire goddess.

Ghosts from a bizarre plane crash and a mysterious underground city point to powerful forces at work inside the Grand Canyon National Park.

A Bigfoot-like creature and UFO sightings suggest that California's Joshua Tree National Park may be ground zero for alien genetic experiments.

Unexplained disappearances, a mysterious death and a Karuk Indian legend may be linked to a race of superhumans in California's Mount Shasta National Forest.