Paleo-European languages
Old European is a designation for the (unknown) languages of the first Neolithic farmers in central Europe, who immigrated from the east around the year 5500 BC. Their original homeland peobably no longer exists: it is drowned beneath the Black Sea, and was where now is the Bay of Odessa. (Before about 5500 BC, the Black Sea was a freshwater lake - the Euxine Lake - with a level much lower than the present day sea level. Then the rising sea burst through the Bosporus and flooded the Black Sea basin within a few years to almost the present day level.)
The Old European languages are not attested in writing (but see Old European script for a undeciphered 'script' that apparently was used in the easternmost parts of the Old European area, which may or may not have been a writing system). The only access to it we have are place names and especially river names that are found all over central Europe.