Book 21 has the story of Alaric’s treasure buried in the river (5c AD), or wait, no, is it Decebalus’ treasure buried in the river Sargentius (2c AD); no, hang on, it’s Audoleon’s treasure buried in the river Sargentius (3c BC) — hmm, probably only one of these stories is true, if any of them. Read: urban legend. River remains unidentified, and of course, none of these three purported treasures has ever been found.
Book 22 mentions toothpicks. An obvious idea, but there’s not much in our literary sources about ancient dental hygiene (other than the nastinesses of tooth powder etc., for which see Smith’s Dictionary, s.v. Dentifricium).
Going back a bit, Book 20 is interesting primarily for confirmation from an unlikely source — the writer of an ancient history himself! — that everybody knows that we don’t read those long-winded rhetorical speeches put by many ancient authors in their characters’ mouths (20.1.1‑5).