Travertine is a white concretionary form of calcium carbonate that is usually hard and semicrystalline. It is deposited from the water of mineral springs (especially hot springs) or streams holding lime in solution. Extensive deposits exist at Tivoli, Italy, near Rome. The largest building in the world constructed largely of travertine is the Colosseum in Rome, Italy. Another notable building using travertine extensively is the Getty Center in Los Angeles, California. The travertine used in the construction was imported from Tivoli. The website of the Getty Center contains more information (http://www.getty.edu/visit/architecture.html) about the use of travertine in its construction, including some videos of travertine being quarried and cut for use.