Mount Nemrut Tumulus is one of nine sites in Turkey inscribed into the UNESCO World Heritage List. Geological investigation was carried out in the field between 2006 and 2009 around Mount Nemrut and its close vicinity. There are statues and horoscopes made of sandstone. The Lower Miocene sandstone covers an area of approximately 0.46 km(2). The sandstone seen at Mount Nemrut is gray, thin-to medium bedded, moderately weathered, weak to moderately strong. Bedding planes are detached both in the field and on the statues. This study investigates the weathering of the sandstone at Mount Nemrut from both field and laboratory observations. The laboratory tests revealed that wetting-drying, freeze-thaw and salt crystallization reduce the strength of the sandstone. In the case of the sandstone, wetting-drying and freezing-thawing give rise to splitting along bedding planes. The wind causes rounding of the sharp corners of the stela. It is seen that two type's sandstones are outcropped. In the field it is difficult to distinguish sandstone types but in the laboratory it is easily detected from their weathering degrees and colors. Dark gray sandstone is found to be more resistant to the ageing tests than the light gray sandstone.