Sonnen is a small municipality in the district of Passau in Bavaria in Germany. It is located in the Danube forest, lower Bavarian forest and is located mostly in the district Passau at a height of 700 to 900 meters. Sonnen lies 28 km from Passau, 9 km from Hauzenberg and from the forest itself 13 km. Sonnen borders with upper Austria which lies onl…Sonnen is a small municipality in the district of Passau in Bavaria in Germany. It is located in the Danube forest, lower Bavarian forest and is located mostly in the district Passau at a height of 700 to 900 meters. Sonnen lies 28 km from Passau, 9 km from Hauzenberg and from the forest itself 13 km. Sonnen borders with upper Austria which lies only 8 km away.