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

Khmer Rouge's high security prison.

A battle between nature and architecture in the Cambodian jungle.

This public square capitalized on a single Eagles reference to bring some life back to an Arizona town.

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

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

Limestone caves with spectacular showcase chambers.

Most-visited and most-photographed slot canyon in the American Southwest.

A spiritual vortex among the red rocks in Sedona.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

Every year, festive decorations appear on this juniper tree located in the median strip of a busy highway.

This 40-room dwelling tucked within a cliff was built by the basin's prehistoric residents.

The first permanent memorial to a unique secret weapon of World War II.

Open since 1938, this diner has kept its fountain, malt machine, and all the gum that greasers left beneath its counter.

A self-built castle made by a mysterious man.

Thousands of Mexican Free-Tailed Bats soar around an abandoned storm drain at sunset each summer.

A museum and tribute to a brave profession.

Every Christmas, one Arizona city makes the most of its dry climate by creating an arid desert tannenbaum.