Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

Ancient pueblos built into the base of a natural canyon wall.

The largest greenhouse in the world is home to over one million types of plants.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Granting the right of way to ships over surface traffic since 1917.

Hear the quietest sound from across the dome.

One man's ambition created this psychedelic log home.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

Native Americans built this circle of stones, which was used to predict astronomical events.

Elevated freight railway turned wildly successful urban park.

A Roman-style column in Oregon hides a spiral staircase inside.

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

An obscure waterfall that looks like something out of a fantasy novel.

A beautiful geyser under environmental threat.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

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

An entire town preserved as a historic landmark.