The largest known Ancient Egyptian obelisk.

The final resting place of the great navigator, or maybe his brother.

Ming Dynasty necropolis raided during the Cultural Revolution.

Monasteries on rock pillars, once accessible only by frayed ropes.

Final resting place of Geronimo, Quanah Parker, and the first atomic gun ever fired.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Macabre astrological automaton clock dating to the late 1400s.

An office built to look like a giant basket.

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 mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Elevated freight railway turned wildly successful urban park.

A priceless collection of the Nation's cryptologic history.

Largest Roman Catholic church in North America.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The United States Capitol's former columns still stand.

The site of the climactic scene from the classic horror film is now a historic landmark.

At 207 feet, one of the world's longest continuous escalators.

Giant granite rocks standing end-to-end like a train of circus elephants.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.