Pamukkale (Cotton Castle), is considered today the eighth wonder of the world. It is presumed that the travertines were formed in the course of a process which lasted 15 thousand years. As the water, having a temperature of 34 degrees Calcius, gushing from the underground springs at an elevation of 160 m off the plain of Menderes, with calciumbicarbonate content, flows down the hillsides, carbonmonoxide gas emanates, and the calciumbicarbonate, dissolving thereby, is sedimented, thus forming the white-coloured travertines. Therefore, the area is called Pamukkale (Cotton Castle).