Postojna is a town and a municipality in the traditional region of Inner Carniola, 35 kilometers (22 miles) from Trieste, in southwestern Slovenia. Population 14,581. The area is known to have been populated since the paleolithic era due to the finding of a cave settlement near the town of Postojna, called "Betalov spodmol". The town lies on the Pivka River. Written sources first mention the settlement in the 13th century and in 1432 it became a borough. It was proclaimed a town in 1909.