John Calvin Batchelor wrote, in a novel, of a place where there are billboards and neon arrows, all pointed to Plato's Cave.
"World's Oldest Continuously Operated Parable, Three Miles Ahead!"
Plato's Cave is a very old parable, to be sure. Not sure it's the oldest, tho. (One presumes we're speaking of the West. I have no clue what the oldest parable is in Asia.)