lori-rocks:

Devetashka cave-Bulgaria by Silvia S.
In the beginning of the 1950s, serious explorations of the cave were held, concerning its transformation into a warehouse. The studies showed that the Devetashka cave used to be inhabited (with some interruptions) during almost every historical era. The earliest traces of human presence date back to the middle of the early stone age before about 70,000 years BC.

(Source: 500px.com)