The only finalist from Europe to make it into the top seven—the Colosseum in Rome, Italy—once held up to 50,000 spectators who came to watch gory games involving gladiators, wild animals, and prisoners.
Construction began around A.D. 70 under Emperor Vespasian. Modern sports stadiums still resemble the Colosseum's famous design.
European sites that didn't make the cut include Stonehenge in the United Kingdom, the Acropolis in Athens, Greece, and the Eiffel Tower in Paris, France.
The Vatican in Rome accused the competition's organizers of ignoring Christian monuments, none of which was featured among the 20 finalists. Archbishop Mauro Piacenza, head of culture and archaeology at the Vatican, called the omission of sites such as the Sistine Chapel inexplicable.
Who do you want to see receive $20,000 to put their Earth-saving idea into action? Check out the ten Green Effect finalists, and until July 20 you can vote—up to once a day—for your favorite idea!