The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

One of London's lost rivers runs through a pipe over the tracks of this subway station.

London’s first road overpass is so old that it was originally built for horse-drawn carriages.

Remnants of cells from the most notorious London prison may lie in the basement of a rare Victorian Gin Palace.

Over several decades, one of London’s most iconic city gates was dismantled, moved out of the city, and then moved back.

Dictionary Johnson’s favorite feline.

The spot where three Protestant clergymen were burned at the stake during the reign of "Bloody Mary."

A theatre built to house the rowdy Oxford graduation ceremonies became the stage for a debate about God's existence.

Hidden in plain sight, this creepy sculpture watches from above.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

Its collection includes a broad array of social, geographic, graphic design, and political history.

This coffee shop lies hidden beneath a historic church.

These Victorian era devil sculptures were designed to spite a local vicar.

The barrel-made lookout from Shackleton's final ship is tucked away in the crypt of one of London's oldest churches.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

The largest collection of historic military firearms in the United States.

The mysterious canine hides atop a drain pipe on the back of the building, some say as a sneaky shoutout to Yale.

Nassau Hall has served as army barracks, a museum, and played a key role in the American Revolution.

The final resting place of many of New Jersey's most famous residents, including U.S. history's most in-vogue antagonist, Aaron Burr.

Six peaceful acres in a residential neighborhood dedicated to art and peace.

This disastrous New Jersey safari park saw animal attacks, escapes, and disease before being abandoned.

This derelict building used to house infirm Freemasons, their widows, and orphans.

A solid steel plane designed to catch fire over and over again.