Editor’s Note: We’ve since expanded our life list to 43 sites around the world for wildlife lovers, adventure seekers and those seeking just a respite from their busy schedules.

Related Content The 21st Century Life List: 25 Great New Places to See

"We are all of us resigned to death: it's life we aren't resigned to," novelist Graham Greene once wrote. A growing number of Americans of all ages are embracing that idea by renewing a resolve to live life to its fullest.

Exhibit A is the recent popularity of "life lists"—itineraries of things to do and places to go before taking the ultimate trip to the Great Beyond. Bookstores brim with titles such as 1,000 Places to See Before You Die, 1001 Paintings You Must See Before You Die and—for the high-minded—Fifty Places to Go Birding Before You Die. A cottage industry of Web sites has also popped up, enabling life list enthusiasts to exchange ideas ranging from learning Japanese to getting a tattoo. Now even Hollywood has gotten into the act, with the release this month of the film The Bucket List, in which two cancer patients, played by Jack Nicholson and Morgan Freeman, break out of their medical ward and embark on a life list road trip that includes dining on expensive caviar and gambling in Monte Carlo.

Life list experts (yes, there are such beings) advise people not to set themselves up for disappointment by trying to accomplish too much. (When's the last time you completed your daily to-do list?) With the entire world to choose from, the maxim "so much to do, so little time" takes on added meaning.

To that end, the staff of Smithsonian—as diverse a group of travelers as you're likely to meet—put their heads together to come up with an exclusive list of 28 places the Smithsonian reader might wish to visit before ...it's too late. Some of the sites are portals into the past—ancient cities so well preserved that visiting them is like stepping into a previous century. Others feature feats of engineering or sublime works of art—or, in the cases of the Taj Mahal and Frank Lloyd Wright's Fallingwater, both. Travelers can visit temples and churches so breathtaking they must have been built with divine inspiration. For the more adventurous, we offer rewards beyond mere sightseeing—from a three-day hike across the Grand Canyon to a ride along China's Yangtze River.

While all of these destinations beckon year-round, there are places where timing matters: many travelers are at a loss for words after witnessing the sun rise over Machu Picchu or seeing Iguazu Falls by the light of a full moon. And, appropriately, some of our sites now confront their own mortality—endangered by pollution or just worn down, like a few of us, by the passage of time.

Whether you visit only a couple of these destinations or all 28, your life will be enriched by the experience. And if along the way you want to gorge on caviar or get a tattoo, that's entirely up to you.

Portals into the Past

Walk the timeless streets and byways of ancient cities on three continents



– Mesa Verde

– Pompeii

– Tikal

– Petra

Feats of Engineering

The world's surviving architectural wonders hewed from stone and mortar beckon as ever



– Pyramids of Giza

– Taj Mahal

– Easter Island

– The Great Wall

A Matter of Timing

Choosing the right year, month or even moment can make all the difference



– Aurora Borealis

– Serengeti

– Iguazu Falls

– Machu Picchu

Triumphs of Vision

Come face to face with history's finest works of art and design



– The Louvre

– Zen Garden of Kyoto

– Uffizi Gallery

– Fallingwater

Scale New Heights

Don't just see nature's most spectacular sites—experience them



– Yangtze River

– Antarctica

– Mount Kilimanjaro

– Grand Canyon

In the Presence of Gods

Encounter temples so magnificent then could only have been built by divine inspiration



– Bagan

– Parthenon

– Angkor Wat

– Ephesus

Here Today, Gone Tomorrow?

Visit these deteriorating or threatened destinations before they disappear



– Venice

– Amazon Rain Forest

– Great Barrier Reef

– Galápagos Islands