An emerald-green grotto just a short trip from Austin.

Most-visited and most-photographed slot canyon in the American Southwest.

An exquisite tunnel of cascading flowers.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

Rippling sand dunes frozen in the Arizona rock.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

One part local history, 99 parts gruesome haunted house.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

A student driver's nightmare.

An unusual round church in London with a Templar past.

A kaleidoscopic warehouse-maze of handmade neon signs.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A visionary, futuristic sculpture in Los Angeles that never met its extraterrestrial potential.

Non-profit time travel mart sells goods you would need for a trip through the fourth dimension.

This former tuberculosis research hospital endeavored to cure the dreaded disease with fresh air and positive attitudes.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

A modern ghost town whose inhabitants were driven away by the growth of nuclear power.