A circular two-story museum built completely by hand with 800 tons of rock.

Right here, members of the Lewis and Clark expedition boiled ocean water to make salt.

Dozens of whimsical bear statues "hibernate" here during the winter months.

According to legend, you must remain completely silent while passing this man-made mound or suffer the consequences.

There's something big lurking beneath the surface of this tiny Oregon park.

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

By day this New Orleans square is for pedestrians, but by night it is a kingdom of kittens.

This small Roman arch was transformed into a dwelling by the founder of the Trinitarian Order.

A colossal aqueduct from the second century B.C., deeply hidden in a gorge on the outskirts of Rome.

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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

The famous sculptor had a hand in this imposing fortress.

The colonial home of Paul Revere during the American Revolution.

A centuries-old church stands as a testament to Boston's "father of architecture."

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

The site of Paul Revere's historic two lantern warning.

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

This exuberantly curated landscape is one of the largest sculpture gardens in Canada.

Its columns were all carved from the same white oak tree.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

An awe-inspiring mosque in Morocco with one of the tallest minarets in the world.

The other side is actually green.