The Planina Polje is located in the northwestern part of Notranjsko Podolje, Slovenia. Annual floods cover the flattened floor of the polje at elevation 445 m a.s.l. and reach the depth of approximately 8 meters. Loamy sediments which were found on surface and subsurface features from the inflow part of Planina Polje up to the elevations of about 495 m a.s.l., indirectly show that floods in the past must have been much more extensive than the recent ones. Radiocarbon dating of flowstone layer from side passage Tiha Jama in Planina Cave revealed that the last such extreme floods appeared around 5,706 ± 49 BP. The time frame of the flood roughly corresponds with the Altithermal (8,000–5,000 BP). More humid mid-Holocene climate might be the main cause for the high floods on Planina Polje.Keywords: geomorphology, floods, radiocarbon dating (14C), Dinaric Karst, Planina Polje, Planina Cave.