Khmer Rouge's high security prison.

5,000 skulls in memorial to those killed by the Khmer Rouge.

A nightmare for the claustrophobic lies hidden in Southeast Asia.

This French colonial post office is arguably the grandest in all of Southeast Asia.

Artifacts and memories from the Vietnam war, located in a place that experienced it first hand.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

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

A beautiful geyser under environmental threat.

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

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

A six-ton, 12-foot-tall concrete prairie dog is touted as the largest in the world.

Dedicated to the history of the 1,000 nuclear missiles that once covered the Great Plains.

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

Every president in history is immortalized in bronze in downtown Rapid City.

One of America's first dinosaur parks gives a window into Depression-era paleontology.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Steep canyon walls hide a forested oasis in the West Texas desert.

This is one really big nut.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

This site honors the end of a 100-year boundary dispute between the United States and Mexico—all started by a river's shifting course.

Old Danish castle immortalized in Shakespeare's Hamlet.

Copenhagen's celebrated theme park and gardens.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.