A stone wall, built 23,000 years ago, was found in the Theopetra cave near Kalambak in Greece. Optically Stimulated Luminescence testing on quartz grains in the stones confirmed that it was constructed during the coldest period of the last ice age. The wall blocked two-thirds of the cave entrance, and may have been used to protect the cave inhabitants from cold winds. The structure gives archaeologists insight into the technological development of humans at that time.
     The cave was continuously inhabited for 45,000 years, from the middle Palaeolithic to the end of the Neolithic period, 50,000 to 5,000 years BP. It was first excavated in 1987.
     
Source: DIscovery News (5 April 2010)