A cave on the Maryland border where civilians took refuge during the bloodiest battle of the Civil War.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

When zealous marijuana enthusiasts kept stealing the "Mile 420" highway marker, the State of Colorado got creative.

Giant telescope mirrors built in a spinning furnace under a college football stadium.

An overlooked memorial honoring the local Washington residents who died in World War I.

An Arizona museum with a collection of pharmaceutical oddities, including a jar of a gangster's chewed gum.

A cabinet of curious mathematical models and old calculators.

Each year, teams of the world's best snow sculptors have 65 hours to create frozen masterpieces.

The outcropping is graffitied with the name of the beloved musical Muppet television series.

This parking garage was the site of what was - at the time - the largest cash robbery in history.

Historic Hull Street was actually the first street with a proper name in the Boston area.

This landmark cemetery in Boston was created more than 300 years ago.

The site of Paul Revere's historic two lantern warning.

The location of one of the first private Catholic schools in the country, providing a valuable sanctuary during the tumultuous period when Protestant and Catholic students were at odds.

This area was once known for being a lawless haven for rough-and-tumble sailors, earning the maritime-themed nickname "the black sea."

The first bell ever cast in Boston was cast by Paul Revere...and sounded terrible.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

The remains of an early 1900s dude ranch that operated until the 1970s.

A rare wayfinding portmanteau of “Street” and “Avenue.”

Once the site of speeding horses, now home to picnickers and public concerts.

This historic Victorian hotel has a scandalous history of affairs and murder.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.