The world's first permanently occupied mountain-top observatory continues to report on the stars.

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

San Francisco Bay's ghost town.

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

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

A giant chess set, minus the psychedelic drug trip.

The headquarters of a secretive order is also a beautifully-designed park.

An extensive collection of ancient Egyptian artifacts and mummies.

Secret refuge and museum of the Duke of Florence.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

The middle finger of modernity.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.