Only known mainland rookery of the threatened Stellar sea lion.

The lush coastal city of Astoria is riddled with forgotten secret sidewalks.

Oregon's unexpected high desert, displaying layers of time in a colorful show.

The magic's in the hole!

New York City's smallest piece of private property.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Home to items never before seen by the public.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

A beautiful geyser under environmental threat.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The anatomical-pathological collection of a man who changed surgery.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Hollowed out cedar log tubs set in an ancient towering forest.

Elevated freight railway turned wildly successful urban park.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A giant Troll lurks under one of Seattle's oldest bridges.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

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