The Obertrumer lake is the largest of the three Trumer lakes, measuring 4,9 sq.km.

The river Mattig flows from south to north through the Obertrumer lake into the Grabensee, and the Mattsee lake runs into the Obertrumer lake by way of a canal.The Obertrumer lake with ist crystal clear waters is ideal for swimming and surfing. Lakeside beaches can be visited in Seeham and in Obertrum.

There are several natural walking tracks around the lake. We can recommend the pilgrimage path „Via Nova“ for experienced ramblers. This trail starts in Metten in Bavaria,Germany and ends in St.Wolfgang in the lakes and mountains area, the Salzkammergut. It leads through the village of Seeham am Obertrumer.