Long buried under the 20th-century landscape, this lift lock of the Alexandria Canal is the lone remnant of an ambitious early American transportation project.

A massive, majestic mammal watches over pedestrians from his perch atop a former B.P.O.E. lodge.

Once the largest trading firm of enslaved people in the U.S., this building is now a museum that preserves Alexandria's dark past.

Once forgotten and built over, this historic Black cemetery now houses a poignant memorial.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

America's first federal monument.

This grave marks the passing of a historic Jane Doe whose identity remains a mystery to this day.

The narrowest house in America is seven feet of pure spite.

I-95's Tijuana-style celebration of kitsch at the Carolina border.

The highest paved road in North America winds its way up Mount Blue Sky in Colorado to an altitude of 14,130 feet above sea level.

This quirky hot springs town known to locals as "T or C" was named after a radio show.

The highest point in Delaware is located under a trailer so this marker across the street will have to do.

A scenic fort on the harbor protected Philadelphia from an attack that never came.

This pun was simply waiting to come to life, and one defense contractor made it so.

This massive swimming pool is the high tech home to the human-powered submarine races.

Mysterious glowing orbs float through the desert night.

This historic boathouse was constructed using salvaged lumber from burned barns.

The first woman to become a member of the parliament of Iceland.

Iceland's tribute to its thankless civil servants.

One of the oldest family businesses in Reykjavík serves lamb-based hot dogs.

Three columns of volcanic rock shoot out of the ocean.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.