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

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

Once thought to be the fabled Holy Grail, it is now known to be an oil lamp.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

This small road tunnel is the only place where you can cross beneath the Erie Canal.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

Where you can hail your favorite fictional commanders-in-chief.

One of the capital's last independent milk bars remains a crucial community watering hole.

This ship carrying cargo and four church bells for the Catedral Metropolitana Nossa Senhora Aparecida ran aground in 1968.

The remains of a 19th-century school and living quarters are perched atop a mountain surrounded by a thick tropical forest.

A toxic ghost town sitting atop a massive coal fire.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

Irontown was founded in 1868, as a second attempt to mine iron from the nearby Iron Mountain.

One of the only places where Earth’s mantle lies above water.

The television series' iconic giant foot was borrowed from this classical painting.

A remarkably well preserved tower dating all the way back to the Iron Age.

Fascination continues to surround one of history's most infamous shipwrecks.

This sandstone gorge in New York State's Adirondack Mountains is home to waterfalls, flumes, and more.

Scattered ruins and a tiny cemetery are all that remain of a failed attempt to colonize the inhospitable Desolate Islands.

An elaborate memorial to a man local legend says died of a broken heart.

This restored house is like a time capsule of the president's unconventional inauguration.

A 19th-century architectural wonder designed by the "father of the skyscraper."