An off-the-beaten path cave with an underground lake.

During World War II this was the site of an "honor camp" used as a prison for draft dodgers, Native American conscientious objectors, and Japanese-Americans—including a man who brought his case against the camp to the Supreme Court.

This church on a Tohono O'Odham reservation has stood since 1797.

360° views of the city plus five floors of optical illusions and hands-on science.

A 19th-century funicular railway shuttles visitors up this surprising sea cliff to one of the world's largest camera obscuras.

A real-life Professor Snape once taught in this Welsh university building, which students of course nicknamed “Hogwarts.”

The longest and tallest aqueduct in Britain can actually be sailed across.

Originally built for London’s cab drivers, this bright green hut now serves anyone a hot drink or meal.

This underground power plant looks more like a super-villian's lair than a public work.

The only remaining historic maritime signal station in the United States.

The pockmarks across the building's facade are remnants of the Blitz.

This is one really big nut.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

An incarceration museum on the spot of possibly the oldest prison in England.

Ship-sized kinetic sculptural fantasy.

This unassuming alcove in London’s famous Tower Bridge once served to capture, store, and display dead bodies from the River Thames.

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

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

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

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

The remains of Crystal Palace Great Exhibition of 1851.

Abstract dinosaur models in London.

Pop culture has helped to keep this iconic British building from being destroyed.

The breadfruit-adorned final resting place of the infamous Captain of the HMS Bounty.