Once the largest windmill outside of Holland, with enormous 114 foot sails.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

A hidden gem, named after a San Franciscan icon, offers spectacular views of the Pacific Ocean.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

Visible below the waves are memorials to the city's Gold Rush dead.

A trash dump made beautiful by nature's power.

This rare example of a "tidefall" is a spectacular drop from the cliffs down onto the beach.

Concrete strongholds stand guard over the Golden Gate.

This lighthouse has been guiding shipping into the Golden Gate since before the American Civil War.

Ride on a fully-restored Nike nuclear-tipped missile elevator from the Cold War.

Though considered an eyesore by some, this boxy Brutalist high-rise plays a significant role in Sydney's past.

In the shadow of the Sydney Opera House, Indigenous ingredients shine.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

"We Seceded Where Others Failed."

The island residents are known for taking their quirky sense of humor with them to the grave.

The world's second largest single-dish radio telescope, once used to contact E.T.

On a clear day, you can see all the way to the Virgin Islands from the top of this observation tower built in the 1960s.

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.