By Rebecca Ruiz

updated 2:44 p.m. ET April 29, 2008

To stand in the shadow of the past is a feeling unlike any other. That's why each year millions travel thousands of miles to see the world's most historic sites.

A monument like the Kremlin — where Peter the Great commissioned a famous weapons depot and Ivan the Great built a cathedral to serve as the seat of the Russian Orthodox Church — is a prime example of how historic structures provide a unique glimpse into a culture's evolution.

Machu Picchu is another. A testament to a civilization's ingenuity, Machu Picchu is a relic of 15th-century urban development. The Incan mountain citadel is surrounded by a tropical forest and is memorable for its engineered roads, buildings and defense walls. While the term "monument" prompts many to think of a general brandishing a sword from the saddle of a horse, Lisa Ackerman, executive vice president and COO of the non-profit World Monuments Fund, encourages travelers to use a broader definition.

"There's no one word that would encompass [these buildings] perfectly," she says. Instead, think of a monument as a place "where civilization has left its mark."

With Ackerman's guidance, we selected 10 must-see monuments on five continents. These structures allow tourists the opportunity to see history through the eyes of a warrior, revolutionary, pilgrim or king, but also act as engines for the local economy, spurring growth as travelers spend money on hotel rooms, meals and souvenirs.

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Keeping history alive
An effective monument, says Ackerman, tells the tourist about local culture and history. The Taj Mahal's breathtaking Mughal architecture, for example, is a tribute to both the beloved wife of 17th-century Emperor Shah Jahan and evidence of Islam's influence during that time period.

The Acropolis — a sacred rock in Athens, Greece, where ancient Greeks built several white marble temples honoring gods — is a remnant of a culture famed for its commitment to democratic practices and philosophical thought.

Istockphoto Built over a period of roughly 1,800 years, the Great Wall of China is the most imposing monument on Earth. Not one single wall, it is actually comprised of many branches that stretch about 4,000 miles.

Though not all monuments make such profound statements, it is important to understand the genesis of a historic site. Judith Dupré, author of “Monuments: America's History in Art and Memory,” suggests tourists read the explanatory plaques and try researching the monument's history before visiting.

Visitors, for instance, might not know that the cultural relevance of the Lincoln Memorial — originally opened in 1922 — evolved in 1939 when an African-American singer was denied a public concert because of her race. Nearly 25 years later, Martin Luther King Jr. delivered his "I Have a Dream" speech on the memorial's steps.

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"That memorial was created to honor Lincoln," says Dupré, "but with the historic concert, it became the country's de facto civil rights memorial."

When it comes to history, Dupré calls monuments "tips of the iceberg."

Monumental moneymakers
Monuments are also economic assets. On trips to such sites, a tourist spends about 8 percent to 10 percent of his budget on admission fees or in the gift shop and the rest in the surrounding community, according to Donovan Rypkema, president of Heritage Strategies International, a D.C.-based economic development and real estate consulting firm. This spending can support hotels, restaurants, roads and jobs in both remote and metropolitan areas.

AP The Palace of Versailles in France, channels the significance of monarchy and royal rule through 17th- and 18th-century French architecture.

A visitor to the Taj Mahal, for example, might spend only $5 for admission to the mausoleum, but further stimulates the local economy by spending $100 on keepsakes at a nearby bazaar and 48,500 rupees ($1,203) per night for a deluxe room at the The Oberoi Amarvilas resort.

"Monuments are great natural incubators," for growth, Rypkema says, because "the economic impact is far-reaching." These sites routinely draw sizable crowds. In 2007, the Statue of Liberty attracted roughly 3.4 million tourists while 4.2 million visited the Lincoln Memorial. Each year, the Great Wall receives about 10 million tourists.

Rypkema says that such traffic supports a fiscal argument for the conservation of monuments. In fact, he urges his clients, who have included the National Trust for Historic Preservation and the National Park Service, to think of a monument's value as enhanced by time instead of diminished and encourages them to invest money in preservation to ensure its long-term worth.

"For cultural resources," says Rypkema, "there's a value that can't be measured by gate receipts and hotel rooms."

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