Taj Mahal, India

Time left... 5 years

With its white marble dome and symmetrical minarets, the Taj Mahal seems like a page torn straight from “One Thousand and One Nights.” Mughal Emperor Shah Jahan’s monument to the memory of his Persian wife Mumtaz Mahal, this brilliant mausoleum took 22,000 artisans and 1,000 elephants some 21 years to assemble. 

The mausoleum itself, like the royal couple whose tombs now lie side by side in a shadowy burial crypt beneath the inner chamber, embodies the marriage of Persian and early Mughal architecture, interweaving marble lattice screens with semiprecious gemstones and lotus motifs.

The Threat:
Owing to heavy foot traffic and poor restoration work, air pollution has been turning the white stone facade into a shade of dirty yellow, and the iconic river that runs through the garden is getting muddier by the day.

Entrance fee $116. Opens 6am-7pm, closed on Friday. Agra, Uttar Pradesh, India, (+91) 562-222-6431. tajmahal.gov.in

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Venice, Italy  

Time left... 90 years

The northeastern Italian city of Venice is lauded for its postcard-perfect facade of gothic architecture and gondolas skimming the surface of an intricate network of canals. Plan your trip around the end of January to early February to catch the Carnival of Venice, a brilliant concoction of theatrical performances and masquerades, with the artisanal masks that have always been part of Venice’s identity. 2017’s carnival runs from Feb 11-28, check out the details at carnevale.venezia.it

The Threat:
It’s real: Venice IS sinking. The “Floating City” has subsided by around 23cm over the past century. While global warming and the increasing frequency of floods have brought sea levels brimming up over the quays, the pumping of groundwater and heavy boat traffic is also dissolving the low salt marsh islands Venice is built upon.

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Glacier National Park, USA

Time left... 20 years

Glacier National Park, a million-acre mountainous territory boasting more than 1,000 species of flora and fauna, is home to a jumbled mix of glaciers at least 7,000 years old. The Blackfeet and Kootenai tribes first set foot in the area around 10,000 years ago, and they’re sharing their knowledge with us still. Check in to one of the five sustainable lodges in the park and wake up to the picturesque vista of lakes and hills—just the indulgence you need after a day’s trekking, rafting or cross-country skiing. You’ll need to make reservations at least six months in advance, as the lodges fill up quick.

The Threat:
There was a time when this stretch of mountains towering across the Canada-US border was blanketed with some 150 glaciers. As a result of global warming, Glacier National Park has around 24 glaciers now; at this rate, we’ll be lucky to see any active glaciers at all by 2030.

Entrance fee $116. Fly to Glacier Park International Airport or take a train to East Glacier Park Station. Montana, USA, (+1) 406-888-7800, nps.gov/glac

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The Dead Sea, Jordan

Time left... 50 years

Staying afloat isn’t an issue in the Dead Sea, which is actually a lake 429m below sea level and 10 times as salty as the ocean—making it far more buoyant, too. You can’t say you’ve done the Dead Sea right without performing the “ritual” of reading a book while bobbing on the waves, legs in the air. Afterwards, slap on the mineral-rich mud along the shore for a free body wrap.