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 naturally mummified 2,000-year-old man.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Bomb tests and sheep ranchers share the world's largest military land base.

This natural wonder is disappearing at an alarming rate.

A surviving remnant of the thick ice mass that once mantled most of Western Canada's mountains.

This futuristic bridge is one of the longest self-anchored pedestrian bridges in the world.

This stretch of beach along California's central coast is a busy highway for the largest seal in the northern hemisphere.

A sculpture of the famous photograph stands on San Diego's "Greatest Generation Walk."

Concrete strongholds stand guard over the Golden Gate.

The tragedy of the Japanese internment camps is remembered here by a stark "Soul Consoling Tower."

Millions of years of oxidation make a drive down this winding Death Valley road surprisingly colorful.

A working model of the entire San Francisco Bay and much of the Sacramento River Delta, complete with regular tides that change every 14 minutes.

This Big Sur waterfall drops 80 feet directly into the Pacific Ocean, and inspired the hillside house up top.

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

The ghost town that ended up on Ebay.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

There is no trying to fall in love with this Star Wars fountain, you just do or do not.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

This electric green sulphur lake in New Zealand looks like a cartoonish radioactive dump site.

Tubing through a cave lit with glowworms is a magical underground experience.