Cave in northwestern Lower Austria. Upper Paleolithic remains are more numerous in Lower Austria. The best known are in the Wachau region, including the sites of the two oldest pieces of art in Austria. These are figurative representations of women, the Venus of Galgenberg found near Stratzing and thought to be 32,000 years old, and the nearby Venus of Willendorf (26,000 years old) found at Willendorf, near Krems an der Donau. In 2005 in the same area, a double infant burial site was discovered at Krems-Wachtberg, dating from Gravettian culture (27,000 years old), the oldest burial ground found in Austria to date. Mesolithic Mesolithic remains include rock shelters (abris) from Lake Constance and the Alpine Rhine Valley, a funeral site at Elsbethen and a few other sites with microlithic artifacts which demonstrate the transition from living as hunter-gatherers and sedentary farmers and ranchers. Neolithic During the Neolithic era, most of those areas of Austria that were amenable to agriculture and were sources of raw materials were settled. Remains include those of the Linear pottery culture, one of the first agrarian cultures in Europe. The first recorded rural settlement from this time was at Brunn am Gebirge in Mödling. Austria's first industrial monument, the chert mine at Mauer-Antonshöhe in the Mauer neighborhood of the southern Vienna district of Liesing dates from this period. In the Lengyel culture, which followed Linear Pottery in Lower Austria, circular ditches were constructed. Copper Age Traces of the Copper Age (Chalcolithic era) in Austria were identified in the Carpathian Basin hoard at Stollhof, Hohe Wand, Lower Austria. Hilltop settlements from this era are common in eastern Austria. During this time the inhabitants sought out and developed raw materials in the central Alpine areas. The most important find is considered to be the Iceman Ötzi a well-preserved mummy of a man frozen in the Alps dating from approximately 3,300 BC, although these finds are now in Italy on the Austrian border. Another culture is the Mondsee group, represented by stilt houses in the Alpine lakes. Bronze Age By the beginning of the Bronze Age fortifications were appearing, protecting the commercial centers of the mining, processing, and trading of copper and tin. This flourishing culture is reflected in the grave artifacts, such as at Pitten, in Nußdorf ob der Traisen, Lower Austria. In the late Bronze Age appeared the Urnfield culture, in which salt mining commenced in the