Haguenau is a commune in the Bas-Rhin department of France, of which it is a sub-prefecture. It is second in size in the Bas-Rhin only to Strasb…Haguenau is a commune in the Bas-Rhin department of France, of which it is a sub-prefecture. It is second in size in the Bas-Rhin only to Strasbourg, some 30 km to the south. To the north of the town, the Forest of Haguenau is the largest undivided forest in France.