Travertine is a sedimentary rock, mostly made of Calcite (Calcium Carbonate), that was generated by the deposit of such mineral from hot water springs and streams pouring from them. The holes are generated either by the gasses trapped by the sediments (the vast majority), or by water plants that were trapped inside the formation and then decomposed. There have tumbled travertine, travertine tiles and slabs, travertine countertops and vanitys, Travertine Mosaic.