Quite simply the largest tree in the world (by volume).

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

This sculpture forces visitors to confront their relationship with space.

A historic casino where Dostoyevsky is said to have lost it all on a single spin of the roulette wheel.

An officers prison camp believed to be impregnable by the Germans saw over 30 successful escapes.

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

An 18th century fountain and two columns are all that remains of Rome's forgotten river harbor.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This large, circular tomb is the final resting place of the first emperor of Rome.

This impressive working clock made of 16,000 plants changes its flowers twice a year.

A sacred Ojibwe site covered in pictographs next to Lake Superior.

Profile of a sleeping person four kilometers long in 250-meter-high cliffs.

This natural wonder is disappearing at an alarming rate.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

Comprised of Spanish war cannons, this sculpture once graced the bow of a WWI warship.

Experience a charming 1930s version of "infotainment."

One of America's most historic homes also holds a startling literary legacy.

Rising 30 feet in the air atop Quarry Hill, the Old Powder House is the oldest stone building in the state of Massachusetts.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

The world-record holder for the longest bridge stretching continuously over water.