Rippling sand dunes frozen in the Arizona rock.

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

Home of one of history's most famous cartoonists just as he left it.

London's largest outsider art museum.

No one knows who created the statues or if they are arranged properly—let alone the artwork's real name.

A once-luxurious, now abandoned hotel in the Italian Alps.

Eco-village hidden in the foothills of the Alps that created a massive system of psychedelic underground temples.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

According to the local folklore, the myriad colors of this lake are the result of a lovelorn wizard's blunder.

Natural cathedral designed by Italian artist Giuliano Mauri.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

This 16th-century monastery has been turned into a surrealist architecture compound.

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

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

Pompeii's less famous neighbor is still revealing her secrets.

A 16th-century horror show built in a lovely Italian garden.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A gorgeous medieval library where the books are kept in chains.

A layered tribute to the work of mosaicist Isaiah Zagar.

Dr Barnes' $25 billion private collection of art and arboretum.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.