Photograph by Michael Nolan, Robert Harding/Nat Geo Image Collection
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Bubbling hot springs and fumaroles fill Furnas Valley, on the Azorean capital of São Miguel Island.

Photograph by Michael Nolan, Robert Harding/Nat Geo Image Collection

Drink volcanic purple tea in the Azores

São Miguel Island is home to mineral-rich hot springs that turn green tea purple, among other weird wonders.

After asking for a cup of “special tea,” the Chalet da Tia Mercês patron is ushered out back to the spigot that protrudes from the wall of the teahouse. Paula Aguiar, who runs the house, fills a clear pot under the running water. At 140°F, the geothermally warmed liquid requires no additional heating for tea steeping. At first, the pot-filling routine falls short of extraordinary, but before long, the clear water begins to turn gray, and then lavender tones appear giving way to a deep purple hue. The green tea—no longer so aptly named—transforms into a mesmerizing shade of violet.

Reacting with the antioxidant-rich green tea, the unoxidized iron and acid-filled content in the unique volcanic water causes the mixture to refract light in a different wavelength—like a prism. The minerals in the water also ensure the tea doesn’t become bitter, even if it over-steeps.

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The purple green tea after seeping on the left and in the early stages on the right.

The purple tea, however, is only one of the many wonders this unusual island group has to offer.

São Miguel is part of the nine-island archipelago called the Azores. Owned by Portugal, this island group in the Atlantic Ocean lies about 900 miles west of Lisbon and 2,400 miles from the United States. While all nine islands have volcanic origins, São Miguel has experienced the most eruptions and earthquakes in the years since. [Experience Lisbon like a local.]

The small town of Furnas on the eastern part of the island of São Miguel looks almost prehistoric—steamy hot springs and fumaroles, boiling water gurgling in mud pools, multicolored geothermal fields, and rippling creeks against a backdrop of bright green mountains and leafy vegetation. Less primeval are the houses dotting the landscape and the paved streets and walkways. The city that’s grown up around the hot springs is reminiscent of a hot tub, the air often filled with a geothermic fog.

“Dotted with bubbling sulfuric caldeiras [springs] and gorgeously manicured botanical gardens, Furnas is a valley of stark contrasts—volcanic vents alongside lush, Jurassic-like vegetation,” says Luis Nunes, founder and CEO of tour company Azores Getaways, which leads tours around São Miguel and the Azores. “Just 40 minutes away from the bustling capital city of Ponta Delgada, visitors can venture deep into the volcanic valley of Furnas and feel transported to another planet.”

The central part of the village is home to nearly thirty thermal water reservoirs of differing temperatures and chemical compositions, most with iron and mineral-rich water. Many of the hot springs, reminiscent of Yellowstone’s, are nested in basins with high levels of sodium bicarbonate, boron, fluorine, and traces of carbon dioxide. For centuries, locals have been using the water from different hot springs for various tasks like cooking, cleaning, and creating herbal infusions. One particular spring always boils a pot of corn, which the locals sell for one euro per ear around the corner. Another area is roped off for making cozido, the local meat stew that’s cooked underground overnight by the volcanic heat. Other springs display warning signs and are fenced off with rocks—these waters are too hot, the gases spewing from them too noxious.

After explorers mapped out Furnas’s hot springs in the late 1700s, locals began pulling waters directly from the springs into their bath houses. In 1866, a wealthy businessman constructed one of these bath houses inside a small summer home overlooking the steaming caldeiras. Today, that house functions as Chalet da Tia Mercês, the “purple tea” house. Two stone-carved bathtubs can still be found in the back of the shop—one originally used by the homeowner’s family and another formerly available for whoever needed a bath. The room is now filled with various types of products: locally grown tea (Europe’s only two remaining tea plantations are both on São Miguel), São Jorge coffee, cheeses from various islands (each makes its own style), pastries and Portuguese muffins, liqueurs, and wines. [Go on a National Geographic Private Expedition in Portugal.]

Aguiar’s life experiences couldn’t be more fitting for her role at Chalet da Tia Mercês. Besides having studied the history of the house extensively, Aguiar holds a degree in environmental sciences with a specialization in thermal resources management. She spent several years studying geothermal activity in Yellowstone before returning to her native São Miguel and getting the concession for the teahouse in 2016.

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The geothermal water transforms the green tea into a deep shade of purple.

“I’ve always liked this house. This house has a lot of history,” says Aguiar. For instance, she says everyone in town knows that the spring behind the house is thought to aid in digestion, according to a priest’s discovery hundreds of years ago. “When I returned to São Miguel, I started working to promote the resources that we have in the Azores. The culture, the chemistry, the biology—all of it comes together here.”

Nobody knows exactly when the purple tea discovery was made, but the bizarre drink is best enjoyed nibbling on one of Aguiar’s homemade baked goods—the banana chocolate pudding cake is cooked underground in one of the nearby volcanic fumaroles—while you watch the frothing hot springs spew steam below you.

Know Before You Go:

Getting there: Delta started offering seasonal direct flights from JFK to Ponta Delgada this summer; Azores Airlines flies from Boston year-round.

When to Go: Spring or summer is ideal, but the weather is actually temperate year-round, and fewer tourists visit in winter.

Which hot springs are best for swimming: “São Miguel is home to six different hot springs and thermal pools for swimming, each with its own unique characteristics,” says Nunes. “We typically recommend our clients plan their itineraries and hot springs visits around the parts of the island they're located on. No visit to Sete Cidades and the west side of the island would be complete without a dip in the natural ocean thermal pool of Ferraria, just as no visit to the summit of Fogo Mountain to see the stunning views of Lagoa do Fogo would be complete without a soak in the Caldeira Velha’s thermal pools. For anyone visiting Furnas, we recommend getting lost in the romantic Terra Nostra Park, where you’ll be able to take a swim in its thermal pool.”

Pro tip: Bring a dark-colored swimsuit as the iron-rich waters will stain light-colored clothing.

Where to stay: If you prefer to remain in the capital city of Ponta Delgada (only 40 minutes away from Furnas), the recently renovated Grand Hotel Açores Atlântico is right on the marina. In Furnas, the recently built Furnas Boutique Hotel and the art deco-era Terra Nostra Garden Hotel both have exceptional spas and well-appointed rooms.

Devorah Lev-Tov is a food and travel writer based in Brooklyn; find her on Instagram @devoltv.
Editor’s Note: A previous version of this article incorrectly implied that items are stored in the stone tubs; they are simply stored in the same space.