Limestone grottoes turns everyday objects into stone.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This amazing pedestrian suspension bridge in the Swiss Alps would give Indiana Jones nightmares.

The alpine falls where Sherlock Holmes apparently met his demise can actually be visited.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

Retirement home for giant obsolete machines.

This small exhibition displays equipment and artifacts once belonging to the feared Stasi secret police.

San Francisco Bay's ghost town.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

The industrial monstrosity known as Bagger 258 is a colossal mining machine built in the DDR - but now left for dead in a German field.

Amazing pre-Civil War ruins alongside a shallow, rocky river that hosts beautiful (but endangered) lilies.

One man's extraordinary topiary garden in a small South Carolina town.

Granite outcropping that the state's tourism bureau doesn't promote because of its delicate ecosystem.

The "last unrestored grand mansion of Savannah" is now a cramped, mouldering maze of antiques.

Despite being burnt down multiple times, the ruins of this South Carolina church are still standing.

Settled in 1696, abandoned after the Revolutionary War.

Beside some power panels, a plaque celebrates the history of an alternate world.

An underground magnet for ever-changing street art.

A modern mechanical planetary system, part of a 10,000 year clock.

Light still pours into the ruins of this ancient Islamic observatory.

Hundreds of hidden passageways weave through the old quarters of Lyon.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

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

Billed as the "largest natural flower garden in the world" this Middle Eastern show field has little competition at 45 million flowers.