Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Gorgeous cave resemble a winter wonderland.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

One of the world's oldest and most massive living organisms is a grove of quaking aspens.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

Three sinkholes filled with warm, crystal-clear water reached by a horse-driven cart on an old train track through the jungle.

The ruins of a medieval monastery built on a perilous slope.

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

A fascinating assortment of cave dwellings, medieval ruins, and sarcophagi are being devoured by the forest.

This ancient altar emerges from the thick forests to reveal the mysteries of Etruscan sacrificial rituals.

Monks turned this mountain into a temple by digging grottoes, tunnels, and a huge pagoda-like hall.

A leafy, peaceful oasis nestled in the heart of Glasgow's busy south side.

Designed to serve primarily the Maharaja, this is an interesting variation on the traditional stepped well.

Trek into the depths of the cave where 17,000-year-old paintings exist alongside 400-year-old graffiti.

The mysterious megaliths have enchanted and intrigued visitors for thousands of years.

A crumbling cliffside ruin hidden in the woods.

A jungle in the heart of São Paulo reminds visitors of what Brazil looked like untouched by man.

This great stone guardian of the forest is a relic from the land's volatile volcanic past.

One of Mother Nature’s geological gems, home to many prehistoric fossils.

This cathedral hides a sculpted dog that determines your fate and an unexploded shell from World War II.

Large-scale contemporary artworks tower over fields and lurk in forests around a Jacobean manor house.

Known as "The People's Park," this verdant oasis is home to elephants and villagers alike.

Once home to a Scottish baronet, this 18th-century historic house doubles as a legendary art space.