Hidden behind Lincoln's head is a 70-foot-long chamber containing enamel plates documenting American history, sealed in a teakwood box in a titanium vault.

The highest point in South Dakota contains the ashes of Valentine McGillycuudy, the "Holy White Man."

One of the largest private collections of fossils in the world.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

A miniature train-ride through Slovenia's largest cave system.

The world's oldest grape-producing vine has survived four centuries of turmoil and even has its own anthem.

This massive subterranean fissure is known as the "underground Grand Canyon."

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

A beautiful drive through the foot of the Alps traces the path of 15th-century Turkish raids.

This one-time health resort was used by aristocrats around the world.

The first declared National Monument in the United States.

This angular Dwarven tunnel cuts through a mountainside in Glacier National Park.

The only road through the heart of Glacier National Park.

Spectacular views await visitors to this lake.

The world's largest Holstein cow.

A fitting attraction for the corn capital of the world.

Giant six-pack could provide one person a six-pack a day for 3,351 years.

One devoted couple has donated multiple recreations of Michelangelo's sculptures to this South Dakota town.

This 19th-century religious artwork was once highly controversial—because it was donated to the church by a divorcee.

More than 7,000 gallons of water pour over these cascading red quartzite waterfalls every second.

This water tower has been a staple of the Rochester skyline since 1931.