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.

This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

The ancient tomb acts as a calendar that keeps perfect time.

An ancient neolithic tomb that only sees the sun twice a year.

This 30-foot pile of rocks may be the grave of a mythological Irish queen.

The oldest inn in Kilkenny was established by the first convicted witch in Ireland.

A sacred well steeped in Pagan roots on the West Coast of Ireland.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

A hugely vast Irish landscape of barren rock that stretches for miles.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.