This Peruvian canyon is filled with geometric salt pools that have been being harvested since the Incan empire.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

A Christian monastery stands on what was once a holy Incan temple.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

Did Inca children also slide down these smooth rocky slopes above Cusco?

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

Death rituals and sacrifice inside a Peruvian megalith.

An Inca spa, military outpost or maybe… both?

A nightmare for the claustrophobic lies hidden in Southeast Asia.

The large collection of pre-Columbian pottery might make you blush.

A pretty park of over 1,600 olive trees that grew from just three saplings brought over from Spain.

This advertisement for talcum powder was painted on the rock face and has since defied removal.

A Civil War Museum with some notable medical antiques.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

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

The span is crooked and made from two older recycled bridges.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

These unusual rooms on wheels are holdovers from the 1960s.

The oldest surviving one-room schoolhouse in Montgomery County, Maryland.

This ruined quarry once produced the distinctive red sandstone used for construction projects in Washington, D.C.

The ruins of this long-abandoned unsuccessful gold mine can still be found.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.