And while tourists are generally a good thing for local economies (they do love to spend cash, after all) some countries are debating whether or not to put a cap on tourist numbers. They're trying to balance conservation and tourism -- not always an easy feat.
Over 10 million people a year visit the 5,500-mile long Great Wall of China. Some tourists are disrespectful and do everything from carving their names in the wall's stones to spraying graffiti.
Cambodia's stunning Angkor Wat temple attracts 2 million tourists a year. UNESCO officials say tourists regularly "step on stones and carvings."
World's tourists attractions are getting ruined
Some of the world's great tourist attractions are being ruined
BEIJING, CHINA - 2000/05/01: A stretch of the Great Wall of China near Beijing shows the effects of years of tourist feet going up and down its steps.. (Photo by Jerry Redfern/LightRocket via Getty Images)
Tourists visit the Angkor Wat temple in Siem Reap province on March 20, 2015. US First Lady Michelle Obama flew into Cambodia at the tourist hub of Seam Reap late March 20, becoming the first wife of a sitting US president to visit the country, part of a two-nation trip to highlight the importance of girls' education. AFP PHOTO / TANG CHHIN SOTHY (Photo credit should read TANG CHHIN SOTHY/AFP/Getty Images)
AGRA, INDIA - MAY 29: Indian and foreign tourists visit the Taj Mahal on May 29, 2013 in Agra, India. Completed in 1643, the mausoleum was built by the Mughal emperor Shah Jahan in memory of his third wife, Mumtaz Mahal, who is buried there alongside Jahan.(Photo by Daniel Berehulak/Getty Images)
Egypt's antiquities chief Zahi Hawass speaks to the media over the linen-wrapped mummy of King Tutankhamun in his underground tomb in the famed Valley of the Kings in Luxor, 04 November 2007. The true face of ancient Egypt's boy king Tutankhamun was revealed today to the public for the first time since he died in mysterious circumstances more than 3,000 years ago. The pharaoh's mummy was moved from its ornate sarcophagus in the tomb where its 1922 discovery caused an international sensation to a nearby climate-controlled case where experts say it will be better preserved. AFP PHOTO/POOL/Ben CURTIS (Photo credit should read BEN CURTIS/AFP/Getty Images)
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India's Taj Majal not only has to fight air and water pollution, but the traffic of nearly four million people a year. The marble and sandstone in some areas of the monument are eroding faster than ever.
And those aren't the only places at risk. The art in the Vatican's Sistine Chapel could be Michelangelo's greatest achievement. But, all the carbon dioxide that tourists breathe out are doing damage. Not only that, but the dirt, dust and yes, skin flakes, that the five million visitors a year sprinkle all over it are also ruining things.
In 2012, the Vatican promised to take a Dirt Devil to tourists saying that they'd "install suction vents to suck dust from clothes" and lower temperatures to reduce the heat and humidity of bodies. Some other sites have gone to even more extremes.
King Tut's tomb in Egypt was closed to tourists completely after moisture from years and years of visitors caused the tomb to deteriorate.
But, experts say that sustainable tourism on a big level is possible and really starts with small actions. So please, don't touch the paintings, don't scribble on the Great Wall like it's a bathroom stall at Hooters, and if a tourist site seems just too crowded, take your dusty pants and skin cells off the beaten path.