Monza and Brianza Chamber of Commerce recently conducted a study of famous monuments and found the Eiffel Tower to be worth around $544 billion USD (or roughly 435 billion euros).
Yahoo! News reports that the study also concludes that the Eiffel Tower is far more valuable than other famous monuments. The Colosseum in Rome was estimated to be worth around $90 billion while Stonehenge in England is estimated to only be worth around $10 billion. The Tower of London was estimated at $70 billion, and Milan's Duomo is estimated at $81 billion.
According to The Telegraph, the study was based on a monument's “image, brand and visibility” among statistical criteria. The study also looked at each monument's tourist index and economic attractiveness index.
The Eiffel Tower was completed in 1889 for that year's World's Fair. The tower was named after Gustave Eiffel, the head of the company that designed and constructed the monument. Although many people considered the tower to be an eyesore at first, the tower eventually gained fanfare worldwide and has since become one of the most recognizable monuments.