Some places keep secrets. In Death Valley National Park, stones appear to slide across the dry ground, leaving trails behind them. Stonehenge, in the U.K., has a reputation as a place of healing. Bring an open mind when you visit the places on our list, and and try to unravel their riddles.

Stonehenge, Wiltshire, England

Nearly a million people visit Stonehenge, in southern England, every year. Many come during the summer solstice. This prehistoric monument is made up of huge stones that may have taken Neolithic builders as long as 1500 years to put into place. Some historians think Stonehenge was a place of healing, while others say it was a temple for worship. Today, researchers believe Stonehenge was a burial site, but mysteries still remain. While the stones in the outer ring may have came from local quarries, the bluestones in the inner horseshoe were probably transported from many miles away. In an age of primitive tools, how were the heavy slabs moved and put into place? And why here?

Ringing Rocks Park, Upper Black Eddy, Pennsylvania

Bring a hammer to Pennsylvania’s Ringing Rocks Park, so you can tap the rocks and boulders piled 10 feet high in this seven-acre field. Most of them will reward you with bell-like tones. Some think the sounds are supernatural, and scientists admit they’re still scratching their heads for an explanation. Although all the stones are made of the same stuff—primarily iron and hard minerals-- only about a third of them vibrate and ring when struck. Geologists suspect the rings may be produced by stresses in the rocks. While they continue their research, local musicians sometimes show up in the park to “play” the stones and jam.

Taos, N.M.

The Taos hum—a mysterious, low-frequency sound heard in this small town, known for its thriving art scene and spirituality--was first reported around 1991. Only some two percent of residents claim to have heard it, and some say it’s more of a whir, buzz or even a deep rumble than a hum. Sophisticated test equipment brought to Taos hasn’t picked up anything to account for the sound, although researchers say it could be coming from ordinary sources, like aircraft or traffic. It’s also possible that “hearers,” as they’re known, have extra-sensitive ears, and they’re detecting sounds the rest of us can’t. Neurologists say the hum might even be an auditory hallucination – not a mental illness, but a product of tinnitus or some other condition. The hum has also been noted in parts of Australia, New Zealand, Indiana, Scotland and England. Most hearers complain that it gives them headaches, disturbs their sleep, and just generally drives them crazy, but others find the mystical hum comforting. According to old folklore, nature herself may be singing in Taos, attempting to restore harmony to the world.

Sedona, Arizona

If you’re looking for beautiful scenery, you’ll find it in Sedona’s red rocks, canyons and hiking trails. If you’re looking for swirling fields of intense energy, you might find those, too, at one of Sedona’s several vortexes. UFOS are supposedly attracted to the vortex at Bell Rock, where people come to meditate and try to connect with a spiritual realm.

While Sedona’s vortexes aren’t visible, they’re said to exhibit a mild magnetism, and people have reported feeling their energy as a tingling on the skin, or a vibration coming from the Earth. Mystical healings have been reported in these so-called power spots. Whatever this strange phenomenon may be, it has earned the vortexes a reputation as sacred places.

Hawaii, the Big Island   

Old Hawaiian legends say that Pele, a beautiful woman with long hair—sometimes an elderly woman with white hair—will protect you if a volcano erupts. But first, you have to give her an offering of flowers, food or even gin. This mystical goddess of fire, lightning, volcanoes and more is said to live in Halema’uma’u crater, atop an active volcano on the Big Island of Hawaii. Many stories describe her fierce temper and passionate personality, and for centuries, people have reported seeing her wander from one island to another. Although Pele may reward or help you if you do something nice for her, don’t incur her wrath by taking lava rocks, shells, sand or other local items. Travelers have been known to mail back their souvenirs after they return home and bad luck strikes.

UFO Watchtower, Hooper, Colorado

Strange lights appear in the night sky in mystical San Luis Valley, where multiple sightings led one resident to build a UFO watchtower on her property. For two dollars per person, or five per car, you can enter the area and climb the ten-foot high structure to look for orbs, discs, flying saucers and other unearthly crafts. No one is sure why aliens would pilot their ships to this particular spot, but there’s not much light pollution here, making it easy for believers to spot unusual crafts.

Be sure to visit the “Healing Garden” at the base of the tower, where psychics claim to have found two vortexes. You can ask the vortexes for whatever you want—but to make it happen, you’ll have to leave something behind. The garden is adorned with all sorts of odds and ends, from ink pens and license plates, to plastic flamingos and hats.

Playa Racetrack, Death Valley National Park, California

Can stones really slide from one place to another in a dry lake bed? For years, scientists have debated how ordinary rocks move around at Playa Racetrack, leaving trails to show how far they’ve traveled. Some speculate that dust devils, paranormal activity or magnetic fields cause the activity. Others say pranksters are shifting the stones, some of which weigh up to 700 pounds, over distances that measure as much as 650 feet. But in 2013, researchers used weather station equipment and GPS devices to record what was really going on. They now think that when ice covering the playa begins to break apart, it's blown against the rocks by strong winds. Then the rocks slide through the mud beneath them. The “sailing stones” are still a rare phenomenon, even if they are moved by almost mystical natural forces.