Europe's largest prehistoric mound – burial site of a legendary king?

The largest stone circle in the world has ended up bringing up more questions than it has answered.

The granddaddy of English geoglyphs dates back to the late Bronze Age.

Human-made caves excavated to hide a secret society of wealthy pagans.

See massive fossils that are over 200 million years old in northeastern Arizona.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

Take shelter from Hawai'i's tropical heat under the massive canopy of largest Banyan tree on the island.

A series of waterfalls and pools that flow through the 'Ohe'o Gulch and into the ocean.

These picturesque Hawaiian falls are home to a rare species of fish that uses a special sucker to climb up cliffs.

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

Dolphins, ancient clams and hundreds of waterfalls make this one of the world's top tourist destinations.

A glacier pocked with ice caves and surrounded by rainforests.

The glacier tucked within a New Zealand rainforest.

Major tourist destination known for its bubbling mud-pools and hot thermal springs.

The once and future home of New Zealand's famed Pink and White Terraces.

Tubing through a cave lit with glowworms is a magical underground experience.

Every equinox this Maya pyramid puts on a spooky ancient light show.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

The largest self-built castle in the U.S., six decades in the making.

The highest bridge in America was built for an almost unnervingly small amount of money.

Once an unstoppable source of gold and silver, this town came to a grinding stop when the groundwater proved deadly.

An experimental, automotive replica of Stonehenge.

Thousands of effigies of Buddha watch from caves set high above a legendary river, plus whiskey.