Travertine is a sedimentary stone from the limestone family. It is made of calcium carbonate and is usually found in the form of deposits near warm or hot springs. Travertine was frequently used in the construction of ancient buildings such as the Roman Colosseum. Its draw back is that it is extremely brittle and porous. You can purchase it with filled pores or unfilled. Most of the travertine tile on the market comes with the pores filled which gives it a smooth even finish. But, due to Travertine porous nature it must be sealed on a regular basis or it will become discolored. It is most commonly used for countertops and flooring, but may also be used in showers and tub surrounds as well as in exterior decor. It must be well supported on a stable floor or cracking will occur.