Travertine is a variety of limestone that forms as a result of fouling and deposit of calciferous fresh water near the falls or on the bottom of the basins. Its name comes from Lapis Tiburtinus "Tibur stone", the ancient name of Tivoli, a town located in Lazio. The ancient Romans used it as a building stone: The Colosseum has been built in Travertine. Despite its granular structure, the Travertine is a very uniform and highly resistant stone: for this reason is one of the most used materials for the construction of public buildings such as railway stations, post offices, monuments, etc.