A Roman-inspired temple once controlled half of San Francisco's waters.

Neither Spanish settlers nor anyone since has been able to tell who built these strange California rock walls.

An extensive collection of ancient Egyptian artifacts and mummies.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

This giant shopping mall still holds signs of its automotive past.

This quaint archive of the silent era preserves and pays homage to a seminal moment in film history.

A burnt orange monolithic dome structure perched on a hillside near Interstate 280.

A classically inspired temple in Redwood City.

One of the largest free-standing structures ever built, this dirigible hangar is now simply a giant skeleton.

From the Difference Engine to the Cray-1, all under one roof.

The world's most famous donkey lives in this pen.

Rodin's famous depiction of Dante's 'Inferno', amidst a sculpture garden of many of his other works.

A hidden world of exotic succulents and cacti.

Guarded by the Angel of Grief, the Stanford family tomb attracts an odd mix of halloween revelry and somber contemplation.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

America's first federal monument.

The United States Capitol's former columns still stand.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

The site of the climactic scene from the classic horror film is now a historic landmark.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

This grand gothic brewery has been pumping out suds for over a hundred years.