The lake museum of Kreuzlingen occupies a converted 19th-century lakeside villa in the Seepark and is the best small museum on the Swiss side of Lake Constance. The collection focuses on Bodensee history, fishing, and shipping, with a strong section on the lake's prehistoric pile-dwelling cultures (a UNESCO World Heritage site of which fragments survive in several Thurgau lakeshore villages).
Other highlights: a working scale model of the 19th-century Bodensee steamboats, photo archives of the lake fisheries, and an aquarium of local species. Small entry fee. Particularly good for a rainy afternoon.