The structure is a stone wall, which has stood at the entrance of the Theopetra cave for the last 23,000 years, probably as a barrier to cold winds.
The wall blocked two-thirds of the entrance to the cave, which is located close to Kalambaka on the north edge of the Thessalian plain.
"An optical dating test, known as Optically Stimulated Luminescence, was applied on quartz grains nested within the stones. We dated four different samples from the sediment and soil materials, and all provided identical dates," Discovery News quoted Nikolaos Zacharias, director of the laboratory of archaeometry at the University of Peloponnese, as saying.
According to a statement by the ministry of culture, "the dating matches the coldest period of the most recent ice age, indicating that the cavern's inhabitants built the stone wall to protect themselves from the cold."
Excavated since 1987, the Theopetra cave is well known to palaeontologists as it was used and inhabited continuously from the Palaeolithic period onwards (50,000 to 5,000 years ago).
"The newly discovered stone structure is important as it shows the technological level of humans at that time," Zacharias said. (ANI)