Not all travelers are on the lookout for sun, sea and the rest.

In a world where 99.9 percent of things can be explained away by science, mysteries are especially exciting, particularly locations that were once inhabited by ancient civilizations.

Here are four of the greatest enigmas on planet Earth.

Easter Island, Chile

The 887 giant Moai rock statues scattered around remote Easter Island, 2,300 miles from the coast of Chile, are believed to have been built by the Rapa Nui. The lightest weighs in at 86 tons, so it’s anyone’s guess how this ancient civilization was able to move them around the island.

The statues’ lack of eyes has led many to speculate that they were placed there by aliens from another planet.

Although we’re unlikely to ever find out how the statues came to be, they do serve as our last remaining link to the demise of this isolated Polynesian culture.

As well as admiring the Moai, visitors can expect to soak up some sun on the island’s two white-sand beaches and take part in activities like snorkeling, diving and surfing.

Yonaguni Monument, Japan

Though it’s one of the largest pyramid structures on Earth, the Yonaguni Monument sits 82 feet below sea level off the south coast of Japan. Discovered in 1986 by a diver, the monument’s origin has long since been disputed by geologists and archaeologists.

The relatively exact proportions and edges of the rock formations have led to lots of theories about how they came to be. Some say they’re the result of natural erosion, while others consider them the remains of an ancient culture.

You can travel to the monument by plane or ship. There are daily flights each morning from Naha on Okinawa Island, while Fukuyama Kaiun runs boats from Ishigaka that take four hours.

Be warned, though: The journey is across open sea, so the waters can get very choppy.

Plain of Jars, Laos

The Plain of Jars is located near Phonsavan, the capital of Xiangkhoang Province. Home to hundreds of stone jars, some up to 10 feet tall, the site was discovered back in 1930 and is believed to be 2,000 years old.

Some believe they were used by an ancient civilization to bury their dead, while legend has it that giants used the jars to store their alcohol, but the truth is no one really knows how or why they were created.

If you’re planning to visit Asia and travelling through Laos, the Plain of Jars is well worth your time. You can take VIP or local buses to Phonsavan from Vientiane, and these take around 10 to 12 hours.

It’s a very popular attraction, so make sure to book a spot on a group tour well in advance.

Nazca Lines, Peru

Less than 200 miles from the Peruvian capital of Lima lies an abandoned, arid plateau with huge ground drawings that measure as much as 660 feet in length.

No one knows why these geoglyphs exist, but the stunning artwork features more than 70 “Nazca lines” and includes detailed animals like monkeys, fish, birds and llamas.

Believed to have been created by the Nazca culture between 600 and 100 B.C., most of the images can be properly appreciated only from above in a plane or observation tower, which makes them all the more remarkable.

What was the purpose of these giant sketches if the ancient civilization had no way of viewing them from above? The mind boggles …

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