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The Golden Gate Bridge took four years to complete and was designed by architects Joseph Strauss, Irving Morrow and Charles Ellis.

While there are certainly plenty of natural wonders scattered throughout the country, we decided to honor the many lesser known man-made structures that showcase the ingenuity of the American spirit.

St. Louis Cathedral
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Among the oldest Cathedrals in America, The St. Louis Cathedral in New Orleans, Louisiana was completed in 1794 after five years of construction.

It remains the seat of the Roman Catholic Archdiocese of New Orleans.

Fallingwater
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Designed by legendary architect Frank Lloyd Wright and completed in 1939, the Fallingwater, or "Kaufmann Residence," is a house located in Mill Run, Pennsylvania.

Widely believed to be one of Wright's best designs, Fallingwater is known as such because of its location: The house sits atop an actual waterfall.

Sundial Bridge
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Built over the Sacramento River in Redding, California, the Sundial Bridge was completed in July of 2004.

Not only does the bridge resemble a sundial, but on the summer solstice — either June 20 or 21 — the bridge actually functions as a sundial.

It was designed by the Spanish architect Santiago Calatrava.

Thorn Crown Chapel
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Located in Eureka Springs, Arkansas, the Thorncrown Chapel was designed by architect E. Fay Jones, a student of Frank Lloyd Wright.

The chapel was commissioned by a teacher named Jim Reed and was completed in 1980.

Our Lady of the Rockies
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Standing at an imposing 90 feet tall, Our Lady of the Rockies is a statue of the Virgin Mary that sits near Butte, Montana along the Continental Divide.

Completed in 1985, Our Lady of the Rockies is the second tallest statue in America, bested only by the Statue of Liberty.

Coral Castle
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Completed in 1920, the Coral Castle was built over a span of over 28 years by Edward Leedskalnin, an amateur sculptor.

Located in Homestead, Florida, the Coral Castle is currently a privately owned and operated tourist attraction.

Her Secret is Patience
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Located at the Phoenix Civic Space Park in Phoenix, Arizona, "Her Secret is Patience" is a sculpture by artist Janet Echelman.

It was completed in 2009 and has won numerous awards, including the "Award for Excellence in Structural Engineering."

Cincinnati Union Terminal
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Located in Cincinnati, Ohio, The Cincinnati Union Terminal (which has been renamed The Cincinnati Museum Center at Union Terminal) was a prominent railroad station in operation from its construction in 1933 to its designation as a historic landmark in 1973.

Biltmore Estate
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Built sometime between 1889 and 1895, the Biltmore Estate is 178,926 square feet privately owned mansion.

Located in Asheville, North Carolina, the Biltmore Estate was built by Guilded Age millionaire George Washington Vanderbilt II.

Hearst Castle
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The Hearst Castle was built in 1919 for newspaper mogul William Randolph Hearst. It is more than 90,000 sq ft, and is considered by many to be a masterwork of architecture.

The Hearst Castle also served as the inspiration for "Xanadu," the fictional compound where Charles Foster Kane spent his last years in "Citizen Kane."

Golden Driller
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Located in Tulsa, Oklahoma, the Golden Driller is a statue of oil worker that stands 76 feet tall.

The Driller has the distinction of being the tallest free-standing statue in the world and the fourth tallest statue overall in the U.S.

Minister's Treehouse
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In 1993, a minister named Horace Burgess received what he believed to be divine revelation that he must begin building a treehouse.

Now, more than two decades later, the "Minister's Treehouse," or "Horace Burgess' Treehouse" as some call it, is unofficially known to be the largest treehouse in the world.

Due to safety concerns, the treehouse is not currently open to the public.

Cloud Gate
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Cloud Gate, also called "the bean" for obvious reasons, is a sculpture by British artist Anish Kapoor and is located in Chicago, Illinois.

It was designed to reflect the Chicago skyline, and was unveiled in 2004. Since then it has become a prominent landmark in Chicago.

Texas State Capitol Building
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The Texas capitol building in Austin, Texas was completed in 1888, based on the winning design selected from a national competition.

It earned a spot on the National Register of Historic Places in 1970, and in 1986 became a National Historic Landmark for its "significant contribution to American history."

It is the tallest capitol building in the U.S., and the largest in gross square footage.

Taos Pueblo
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Taos Pueblo, located in northern New Mexico, is a series of colorful adobe buildings that have been inhabited for over 1000 consecutive years.

Taos Pueblo functions as a thriving Native American community, a World Heritage Site and a National Historic Landmark.

BP Pedestrian Bridge
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This pedestrians-only walkway is the first bridge designed by architect Frank Gehry.

Located in Chicago, Illinois, the bridge has curves and metal siding creates a sound barrier, dramatically reducing noise from the traffic on nearby Columbus Drive. The bridge is 935 feet long in total.

Hotel del Coronado
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The Hotel del Coronado, located in Coronado, California, has over 125 years of history. It has hosted guests from Charlie Chaplin to multiple U.S. presidents and the rumored ghost of one Kate Morgan.

It serves as both a resort and a National Historic Landmark today. It is one of the few surviving wooden Victorian beach resorts and the second largest wooden building in the U.S.

The Keeper of the Plains
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The Keeper of the Plains was designed by native American artist Blackbear Bosin and constructed by Tom Washburn. It is located in Wichita, Kansas.

At 44 feet tall, it is one of the fifteen tallest statues in the United States. It was elevated another 30 feet onto a rock promontory in 2006.

Old Faithful Inn
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Old Faithful Inn is the largest log structure in the world and a national historic landmark.

It has over 300 rooms and is the most popular lodge in Wyoming's Yellowstone National Park. It was built in 1903-1904 entirely from local logs and stone and is still offering tours today.

Bixby Creek Bridge
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The Bixby Creek Bridge is 260 feet high, 700 feet long, and is considered the most scenic (and most photographed) stretch of road along the California coast.

Located in Big Sur, California, rights to build were given to Ward Engineering Co. for $202,334 in 1931. The bridge was completed in 1932, although it was not open to traffic for another five years.

US Air Force Academy Cadet Chapel
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The US Air Force Academy Cadet Chapel was completed in 1963. Its goal is to to "inspire men and women to become leaders of character through spiritual formation," according to the chapel's website.

The chapel, which has seventeen spires that can be seen from miles away, was designed by Walter A. Netsch Jr.

Tours and regular worship services are open to the public, and the chapel boats over half a million visitors annually.

House on the Rock
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The House on the Rock is the brainchild of Alex Jordan, and was built as an artistic retreat in 1945. Since then it has become a tourist attraction and is known for its eccentric rooms and collections.

The house boasts The Infinity Room, which extends 218 feet long and 156 high over the valley floor without supports (pictured), and the World’s Largest Carousel which contains 269 handcrafted animals, 20,000 lights
and 182 chandeliers among other things.

Spiral Jetty
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The Spiral Jetty, located on the northern side of the Great Salt Lake in Utah, is an earthwork piece created in 1970 by artist Robert Smithson.

The jetty is 1500 feet long, 15 feet wide and made entirely of basalt rocks and earth from the site. The jetty changes season to season, based on the water levels of the lake, which gives it its artistic appeal.