Famed architect Antoni Gaudi built this generous thank you gift to a friendly host who housed him during a job.

The largest greenhouse in the world is home to over one million types of plants.

A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

Volcanically heated hot springs.

Rustic natural hot springs in the deciduous rain forest.

Hollowed out cedar log tubs set in an ancient towering forest.

This Japanese-inspired labyrinth of hot springs is hidden in a Chilean forest.

Geothermal waterfalls in Tuscany.

Roman ruins top white travertine terraces formed by ancient hot springs.

Every autumn, this hillside is ablaze with red summer cypress.

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

A stunning silver lining to global warming's gloomy cloud.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

Medicinal spa created with the discharge from a geothermal energy plant.

A seemingly endless landscape of pure salt stretches far across Bolivia.

An Australian lake whose pink hue defies scientific explanation.

A gargantuan crystal kingdom.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A perfect turquoise lake colored with glacier dust.

A breathtaking bridge that crosses a vast gorge over a river's torrents, and has a tale of a devil architect attached.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

An emerald-green grotto just a short trip from Austin.

World's largest cave was only discovered in 1991, and now offers tours to the public.