Ancient ruins hidden underneath a modern luxury hotel.

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

An 18th-century post box used to alert the church of sick and ailing foreign pilgrims.

The Pope’s secret escape route.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

A massive marble foot is tucked away in a small alley near the Pantheon.

Abandoned silver mine strewn with wrecked and twisted structures.

An enthusiastically interactive mining museum that won't let black lung ruin the fun.

In the 1950s, two women saved this grand theater in the Colorado mountains from demolition.

Once an unstoppable source of gold and silver, this town came to a grinding stop when the groundwater proved deadly.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

The phrase "the shot heard around the world" was coined after a skirmish at this bridge.

This location holds the truth to what truly happened that faithful night.

The oldest continuously operating fish market in the United States.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

Decades before the scandal, this staircase on the river was a literal "water gate."

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

This grand gothic brewery has been pumping out suds for over a hundred years.

A tribute to Ponce de Leon's supposed quest for eternal youth.