Approximately 28-30% of the land is plain, 25% is high plateau and tableland, and 47% is mountainous. At 2571m Mount Honaz is the highest in the province, and indeed in Western Anatolia. Babadag in the Mentes range has a height of 2308 meters. The biggest lake in Denizli is Acıgöl, which means bitter lake and indeed industrial salts (sodium sulphate) are extracted from this lake which is highly alkaline. There is a thermal spring to the west of Sarayköy, at the source of the Great Menderes River, which contains bicarbonates and sulfates. There is another hot spring in Kızıldere which reaches 200˚C.