Le storie più antiche vengono tramandate di generazione in generazione.

Tramandare is a first-conjugation regular verb meaning “to hand down” or “to pass on” (usually stories, traditions, knowledge). In the active voice you’d say for example:

• I genitori tramandano le storie ai figli.

Its principal parts are: tramandare – tramandato – tramandando.

Italian has two common ways to form a passive:

1. Essere
   • participle (e.g. sono tramandate) – often describes a state resulting from the action.
2. Venire
   • participle (e.g. vengono tramandate) – emphasizes the action/process itself (“they are being passed down”).

In our sentence, vengono (3rd pl. of venire) plus tramandate (past participle) literally means “they are conveyed/passed down.”

You could also use the si-passive:

• Le storie più antiche si tramandano di generazione in generazione.

Più antiche is a relative superlative, meaning “the oldest (of all the stories).”

• If you used antichissime (absolute superlative), you’d mean “very/extremely old” rather than “the oldest.”

Both are grammatically correct, but they carry different nuances:

• Le storie più antiche = the ones that are the oldest in a given group.
• Le storie antichissime = stories that are extremely ancient, with no comparison implied.

Adjectives that express quality or comparison—like più antiche—typically follow the noun in Italian. This ordering:

• le storie più antiche (preferred)

is more idiomatic, though you can also say

• le più antiche storie
  to put more emphasis on “antiche.” The meaning stays the same; the difference is a slight shift in style or focus.

Di generazione in generazione is an idiomatic expression meaning “from generation to generation.” The preposition di combined with in here highlights the passage through successive generations.

You might also encounter da generazione a generazione, which is equally correct but slightly less common in this fixed phrase. Both convey the same idea of continuity over time.