Highly spherical boulders on the shores of New Zealand.

The premier place to experience the Victorian imagining of the steam-powered future.

One of the world's steepest streets seems to have houses sliding down it.

Major tourist destination known for its bubbling mud-pools and hot thermal springs.

The glacier tucked within a New Zealand rainforest.

This strange geological landscape erupts with sudden bursts of water.

Known for the tunnel that leads visitors to the water.

A perfect turquoise lake colored with glacier dust.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

This indoor ski resort has a mountain contained inside a mall.

This African beach is home to thousands of rare mainland penguins that are known for their annoying voice.

Where artisans use centuries-old techniques to build traditional Arabian ships.

This beautifully restored fortification kept the city safe for centuries.

This spectacular mosque houses the second-largest chandelier in the world.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.

Cleveland's giant "free" stamp is a nod to the Civil War, but was misinterpreted for years.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

World War II bunker still standing on the New Jersey beach.

The rusting remains are visible sticking out of the waters of the Delaware Bay.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.