HERISAU, a town in Switzerland, capital of Auster-Rhoden, at the confluence of the Glatt and Brühlbach, 7 miles N.W. of Appenzell, 2334 feet above the sea-level. The town is very irregularly built. The church tower is the oldest building in the canton, and is supposed to have been built in the 7th century. The archives are kept in this tower. Herisau has a public library, courthouse, arsenal, and an orphan asylum. The neighbouring heights, two of which are crowned with the ruined castles of Schwanberg and Rosenberg, afford beautiful walks. It has important cotton, muslin, and silk manufactories, and carries on an extensive trade. The baths of Heinrichshad are a mile distant. Pop. 2700.