On our trip to Greensburg, IN we were in a driving mood and visited surrounding towns as well. One of which was Oldenburg. We sort of stumbled upon it - just turning on back roads whenever we felt like it.
They're really known for their Freudenfest in July - and seriously you should go to the website just to hear a German/English version of "In Heaven There Is No Beer" - good stuff.
They have a pretty fun mural on one wall of the town sights.
Why Should You Go? It's a small little pub and the staff was very friendly. The food was pretty good - a little better than I expected and I hear the Rueben is killer.