This pump on the bad side of Victorian London betrayed a horrifying revelation about the water supply.

The commemorative stone column conceals a secret laboratory.

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

A memorial for public executions that dates back to the 14th century.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

There's an exclusive Beefeaters pub hidden in the Tower of London.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

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

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

A mysterious suspended hand greets unsuspecting visitors at the Tower of London.

Locals call it the "Give Peas a Chance" bridge because of its distinct graffiti.

On October 17, 1814, a 15-ft. wave of beer ran rampant through the streets of London.

A measuring mishap led to these artificial stone ladies losing their stomachs.

One of only two commuter aerial tramways in the United States.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This is the oldest Roman-made bridge in the city still existing in its original state.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

This demon atop the Notre-Dame de Paris looks utterly bored.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

Ample proof that watery ends make for well-preserved, millenia-old mummies.

This colossal war machine is now a living museum dedicated to underwater warfare.