Water

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

This traditional garden in the San Fernando Valley doubled for Star Fleet Academy, and is irrigated entirely by wastewater.

One of the world's tallest waterfalls wasn't revealed to the world at large until 2006.

This small oxbow lake has rare giant river otters and some Seussian-sounding birds.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

A little-known hot spring haven right below the highway.

It's 2 billion years old!

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Eight "Guardians of Health" protect this art deco water tower from pollutants and bacteria.

One of America's first planned communities is preserved in a state park.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.