The first museum in the U.S. to address human rights issues in China.

This house was once the location of Frelinghuysen University.

The hippo that stands on this university campus was once a drunken flea market purchase.

Stone markers on the campus of Gallaudet University commemorate a peculiar school tradition.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

The highest point in Maryland is only accessible by hiking through another state.

A remarkable time capsule of American manufacturing deep in Maryland coal country.

The first blast furnace in the United States that used coal and coke fuel instead of charcoal to make pig iron.

This beautiful stone arch bridge wasn't even expected to stand for one day, but people have been crossing it for centuries.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.

Maryland's first (and last standing) toll house on America's first federal road established the state as the "Gateway to the West."

This one-room cabin where the young colonel slept during the French and Indian War.

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

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

This advertisement for talcum powder was painted on the rock face and has since defied removal.

One of the only memorials dedicated to journalists who died in combat.

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

Bizarre Cavern.

Unannounced visitors are now welcome at the site of the largest Prohibition-era bootlegging operation in the region.

First built around 1848, this bridge was destroyed by arson, but original timbers are included in the replacement.

This four-story steel sphere in Maryland was used to test biological weapons.

This hidden treasure provides a charming access point along the south side of Baker Park.

According to local history, this cast-iron canine was nearly melted down for bullets during the Civil War.