Experts say the biofilm which has darkened landmarks in the US can also be found at numerous sites thousands of miles away, including Hadrian's Villa in Italy and Angkor Wat in Cambodia.
http://www.dailymail.co.uk/sciencetech/article-3755194/The-creeping-black-slime-taking-historic-building-world-Researchers-reveal-monuments-Washington-Angkor-Wat-hit-impossible-remove-biofilm.html