Mounds of fine golden sand that can rise nearly 500 feet tall.

An underground world of gorgeous, palatial metro stations designed as a nuclear shelter complex.

The ancient heart of Tunis is an enormous maze of narrow streets and alleyways.

This colorful creation wasn't always a welcome part of Toronto's Moccasin Trail Park.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

Home to the longest wooden escalators in the world.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

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

The Avenue of Mausolea is a series of grand palatial tombs.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

This strange portrait of six ladies with chicken bodies commemorates a count's dirty habits.

The tomb of history's greatest potato promoter is surrounded by tubers.

This Soviet-era athletic and recreation facility is the highest ice skating rink in the world.

This Soviet statue is based on a piece of propaganda that's been elevated to national myth.

World-famous, Pink's still manages to keep its prized cult fetish status.

This remote island village was in danger of depopulating completely until a tunnel was built to connect it to the rest of the world .

Largest Kauri tree in New Zealand.

A small alleyway with an unusual moniker.

The most beautiful Taco Bell in the world even has surfboard parking.

Modern art meets modern convenience in possibly the world's most architecturally important public bathroom.

Over time, this castle grew to encompass the entire island.

A KFC honors an eighth-century Chinese poet with holograms and verse.

Ado Awaye Mountain and the unique lake that sits near its peak are shrouded in ancient legends.

Each of these hand-painted wooden boxes, which date to between the 16th and 19th centuries, contains a genuine human skull.