[Erasmus]

It depends on era from which you choose the dialect. The "t" and "th" are both pronounced "t." The word means "Neander Valley."

Additional useless bit of trivia. Our word "dollar" comes from "thaler" or "taler," which was a mediaeval coin minted in (and with silver mainly from) the Joachimsthal, in Bohemia.

[Straight Vermonter]

That is the modern pronunciation. A century ago the th had the other pronunciation in German.