Genesis of modern hydroelectric power.

A building so large that it has its own weather.

Steepest flood safety railway in the entire world.

Memorializing an American tragedy of massive proportions.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

The statue of John Harvard isn't actually John Harvard—or even, technically, the founder of the school.

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

Once America's longest-manned military fort, now an abandoned hulk.

Oldest synagogue in the United States.

Experience a charming 1930's version of "infotainment."

The crown jewel of the Queens Museum is a nearly 10,000-square-foot architectural model of the city originally built for the 1964 World's Fair.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

A collection of artifacts from Maryland's maritime past.

Once America's tallest structure, now a Baltimore landmark.

This church built atop a gas station promises to "equip you for the next stage in your life’s journey."

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

Parking garage where Bob Woodward met Watergate source "Deep Throat."

America's first federal monument.

This campus chapel is Robert E. Lee's final resting place and a topic of debate about the legacy of the Civil War.

Few other hotels can rival the grandeur of the Castle in the Rockies.

A historic coal mine that doubles as a museum and tourist attraction.

The New York hotel where tragic visionary Nikola Tesla spent his final hours, destitute and alone but for the pigeons.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.