This war hero's old shop remembers the fine line between medicine and quackery during the Revolutionary War.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

An ancient underground cultic temple where sunlight penetrates on the summer solstice.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.

60 feet of towering steel balances gracefully.

The legendary building that needed ghostly approval before being built.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

Built by the patriotic residents of Boonsboro in a single day.

The ruins of an ancient city built by Mayan traders is centered around a temple of a sacred feathered serpent deity.

Three sinkholes filled with warm, crystal-clear water reached by a horse-driven cart on an old train track through the jungle.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Elevated freight railway turned wildly successful urban park.

Home to the deepest rift anywhere on Earth.

This two-room shotgun shack in Tupelo is the birthplace of a King.

Kentucky, Tennessee, and Virginia meet at this point in the Cumberland Gap.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

An artsy hidden staircase leads to breathtaking views of San Francisco.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

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