Toledo's German-American Festival is a big, unapologetically social summer event at Oak Shade Grove in Oregon, just east of the city. It is built around German food, beer tents, folk dancing, music, and the kind of community-club energy that makes more sense in person than on a poster.
Go for an evening rather than a quick look. The festival is most useful to travellers when it lines up with your dates, giving Toledo a lively cultural stop beyond museums and riverfront sights. Check the current schedule before setting out, since it is an annual event rather than a daily attraction.