This forgotten boat elevator was an engineering marvel in its heyday.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

A much-maligned monument to teetotalism.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

The national park was once a plantation estate.

The most decorated dog of World War I is preserved in the Smithsonian.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

This mostly abandoned shopping outlet is now adorned with beautiful graffiti and murals.

Mysterious hillside with a continuously burning natural fire.

An 18-meter-long sarcophagus of a constantly growing dead prophet.

This "tower of death" has acted as an observatory, a religious hub, and an executioner's lair.

Light still pours into the ruins of this ancient Islamic observatory.

The Avenue of Mausolea is a series of grand palatial tombs.

A refurbished locomotive from a bygone era in the middle of the Jordanian desert.

This ancient stone necropolis is in danger of disappearing.

An oasis of shade and color amidst the bustle of the old city.

Known as the "Valley of the Moon," this Jordanian wadi is one of the most amazing desertscapes on Earth.

This exceptionally well-preserved ancient marvel also houses a small museum dedicated to Jordanian folk tradition.

An ancient capital city that dates back 3,000 years and harbors many surprises.

Within the Saudi Arabian desert lies a 2,000-year-old ghost town made of stone and mud.

More than 100 monumental tombs carved into rock are preserved at this ancient Nabataean site in the Arabian Desert.