Boyd’s Bible Dictionary:
(pitted vale). A vale, full of slime-pits, supposedly near the Dead Sea, in which the kings of the plain cities met their invaders (Gen. 14:1-10).
Concise Bible Dictionary:
One passage reads “the vale of Siddim, which is the salt sea;” and another the vale was “full of slime-pits,” that is, bitumen springs (Gen. 14:3,8,10). It was doubtless near the Salt Sea, but is not identified.