Top 10 Most Controversial Historical Sites

One of the world's most infamous prisons -- touted as inescapable -- is located in the middle of San Francisco Bay, but the penitentiary is only one part of the island's history. After operating for 29 years as the United States' first maximum-security prison and drawing public fascination thanks to notorious inmates like Al Capone, the prison closed. The island then sat empty for more than six years until a group of Native Americans tried to claim the land in 1969. After they'd lived on Alcatraz Island for 18 months, federal marshals removed them, but many still consider the occupation a pivotal moment in the American Indian movement because of the national attention it brought to the cause.

With such a storied past, it's easy to understand why Alcatraz Island remains fascinating to thousands of tourists who flock to the island each year to get a look at Capone's cell, Native American graffiti and many other features, including a bird sanctuary and the West Coast's first lighthouse.

Way up in the hills of South Dakota is a massive monument honoring four of the United States' most influential presidents. At first glance, this homage to American history doesn't appear controversial, but many Native Americans, who consider the land a holy place, would disagree. The U.S. government promised the land in perpetuity to the Lakota Sioux tribe in 1868, but took it back years later during the Gold Rush. Then, in 1927, the government approved what is now the Mount Rushmore monument. That move added insult to injury for the Sioux tribe, which felt the government was not only taking over its land, but desecrating it, too. In response, the Lakota Sioux tribe began carving an even bigger monument about 20 miles (32.2 kilometers) from Mount Rushmore to memorialize Crazy Horse -- a Lakota warrior -- in 1948. This monument is not without its own critics, who believe it desecrates sacred land; plus, there were reportedly no photographs ever taken of Crazy Horse, and many question the authenticity of the sculpture. Nevertheless, construction continues.

Built by King Herod in 20 B.C., the Western Wall in Jerusalem is considered the holiest Jewish site in the world. It was originally part of an enclosure for the Temple Mount, but the Romans destroyed the temple in 70 A.D., and the wall and an underground tunnel were all that remained. Only a few hundred worshippers could pray at the wall at any given time until a plaza facing it was built in 1967. Now, thousands of worshippers and people of all religions make the pilgrimage every year to leave written prayers in the cracks of the wall.

While the wall is a place where people come in peace, a fight has been brewing for some time over the origins of the wall and its rightful owners. Leaders of Islam deny the wall's Jewish origins and claim it belongs to Muslims. Meanwhile, the Jews don't claim ownership of the wall, stating it does not belong to any one group or religion, but to God.

On the outskirts of Ho Chi Minh City, there is a complex tunnel system that stretches for more than 120 miles (193 kilometers) and is unlike any tunnel ever built. It took the Vietnamese more than 20 years to complete the Cu Chi tunnels, with locals using small tools and their bare hands to dig them. During the Vietnam War, these tiny passageways became an underground city for the Viet Cong and citizens seeking shelter from bomb raids. Outfitted with living quarters, the tunnels were where the Viet Cong ate, slept, took cover and carried out attacks on U.S. forces, and they proved to be a major source of consternation for American troops.

The tunnels were once so small that soldiers had to crawl on their stomachs to traverse the complicated passageways. Now, they've been widened for visitors, but you'll still have to crawl on your knees in order to navigate through the system. The Cu Chi Tunnels are a considered a must-see attraction for anyone visiting Vietnam, but some question if it's appropriate for concession stands and souvenir shops to be set up where so many Vietnamese lost their lives.

The Big D is well known for cowboys, J.R. Ewing and football, but it's also known for a tragic event in America's history: the assassination of President John F. Kennedy. Kennedy was shot while riding in a presidential motorcade through Dealey Plaza in 1963. Witnesses claimed to have seen a man in a window of the Texas School Book Depository, and police later discovered a sniper's nest and rifle on the sixth floor, leading them to the alleged shooter, Lee Harvey Oswald.

The depository became a symbol of hate, and many locals wanted it demolished. Instead, the sixth floor is now a museum dedicated to Kennedy and the events surrounding his assassination. Some areas of the sixth floor have been restored to their original appearance in 1963, and visitors can view more than 400 photos and artifacts that reconstruct the political scene of the early 1960s. The assassination is still the subject of many conspiracy theories, and millions of visitors travel to Dealey Plaza every year to remember Kennedy and get a glimpse of where his killer stood.

The U.S. military dropped the first atomic bomb in world history in Hiroshima, Japan on August 6, 1945. The bomb instantly killed thousands, with a total casualty count of 140,000 people. A once-thriving metropolis, Hiroshima was flattened by the bomb except for a few buildings -- one of them the domed Hiroshima Prefectural Commercial Exhibition Hall. The Hall retained some of its walls and the steel frame of the dome; this structure quickly became a symbol of survival and rebuilding. The building is now known as the A-bomb Dome and is the main attraction at Hiroshima Peace Memorial Park. The domed building was intentionally left in its original condition to remind visitors of the effects of nuclear war. The building is particularly striking at night, when an eerie green glow washes the outer walls of the frame and a red light emits from inside to signify the atom bomb and those lost to it.

At the very center of Tibet is the capital city of Lhasa, and in the middle of Lhasa is the heart of Tibet, the Potala Palace. This extraordinary building was erected more than 13 stories high on a mountain face and stretches more than 1,000 feet (304 meters) along a snowcapped ridge. Its gold towers can be seen 12 miles (19 kilometers) away, and for more than three centuries, this spectacular building served as the residence of the Dalai Lama, as well as a monastery, mausoleum and governmental offices. That all changed in 1959, when the People's Liberation Army of China ousted the Dalai Lama and took control of Tibet and the palace. Now, this once sacred place is a museum with more than half a million tourists visiting annually.

Once the world's tallest buildings, New York City's original World Trade Center (WTC) towers were built in the late 1960s and became a symbol of financial freedom. They were also targets for terrorist attacks. In 1993, a van loaded with explosives was detonated in the garage of the north tower, killing six people and injuring more than 1,000. Then, on September 11, 2001, two commercial planes struck the towers, causing them to crumble soon after. The attack resulted in more than 3,000 deaths and sunk the entire nation into a state of shock and grief, but soon, talks of rebuilding began.

Many New Yorkers believed the site should be treated as sacred ground to those who were lost, while others wanted to rebuild bigger as a sign of defiance to terrorists. After several years of debate, a plan was approved to include a memorial and new office buildings at the site. However, that wasn't the end of controversy over the WTC site. In 2010, plans to build a new Islamic community center two blocks from the WTC site pushed the nation into another emotional debate about what's appropriate at the site of the largest terrorist attack on American soil. On Sept. 11, 2011, the National September 11 Memorial & Museum opened to the public and in 2014, the rebuilt World Trade Center opened for business.

One of the largest public squares in the world is also home to one of the world's largest cover-ups. In the spring of 1989, Tiananmen Square became the site of the largest anti-government protest in the 20th century. When political leader Hu Yaobang died, it triggered millions of students to fill the square to demand the kind of democracy Hu symbolized. After seven weeks of protests, the People's Liberation Army took control of Tiananmen Square, killing hundreds and injuring thousands. Since then, the Chinese government has continued to try to cover-up the events, and even on the 20th anniversary in 2009, it blocked Internet access to any information about the event and wouldn't allow foreign journalists access to Tiananmen Square.

The city of Oswiecim, renamed Auschwitz by the Third Reich, is home to the concentration camps established in 1940 and has become the symbol of genocide and the Holocaust. There are two camps here, the main camp known as "Auschwitz I" housed between 15,000 and 20,000 prisoners. The second camp, called Birkenau or "Auschwitz II," was the larger of the two camps and held more than 90,000 prisoners by 1944. It's difficult to know how many people died at Auschwitz. Some estimate about 500,000, while others think it's millions. But thousands of prisoners did survive and were witnesses to the crimes committed there, though some groups continue to deny the Holocaust ever happened. The camps reopened in 1955 and each year host more than a million visitors, who can bear witness to tragic events by way of photographs, artifacts and survivor stories.