Gold Rush ship-turned-hotel buried underneath San Francisco's financial district.

2300-year-old Roman road connecting the empire.

The glowing blue Nymphaeum of Emperor Tiberius.

Ancient snack bar of the Roman Empire re-opened.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Erotic art covers the walls of the largest ancient pleasure palace.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

The world's largest wooden structure.

Spain's stunning solar energy plant.

The final resting place of the great navigator, or maybe his brother.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

An ancient Egyptian temple in the middle of Madrid, Spain.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

The bat-covered home of one of the world's most popular brands of rum is located on a tropical Art Deco campus.

This former sugarcane transport tunnel is now a portal to a lovely beach.

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

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

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

A former waterfront market is now in the center of town due to some interesting Boston engineering.

The 15-foot-wide, 2-ton pan fries hundreds of chickens once a year.

In upstate New York, gorgeous waterfalls and a watermill are slowly being reclaimed by nature.

This small road tunnel is the only place where you can cross beneath the Erie Canal.