Is there a one-word, more formal adjective for the expression "as old as the hills" ?
The idea is that there is something very old but a little forgotten today (and usually one uses this expression when speaking to someone who doesn't know about the thing).
Example sentences : "This soup is great, you really need to tell us the recipe!" "It's nothing original you know. The recipe is (missing adjective here). The Romans already knew about it."
"There's civil war again in region X, I am a little surprised." "You know, the enmity between ethnic groups Y and Z there is (missing adjective here). We have historical records from ten centuries ago"