At the mouth of the Berchtesgaden National Park, surrounded by the Alps, lies Königssee. This 8 km long, 1250 m wide and 190 m deep lake is a must-see while visiting Bavaria.
Since 1909, only electric boats have been allowed to roam the waters of Königssee lake, hence the high water quality. Boat tours are offered, which last about an hour and allows passengers get off to explore the St. Bartholomae church and Obersee - another lake at the last stop of the tour. The returning boats run quite frequently, but be sure to check the schedule, since it's a really long trip back to civilization from both stops.
After exploring, you can visit the lakefront village with restaurants offering native Bavarian food, delicious beer, and the opportunity to unwind before your return trip.
Königssee Lake can best be reached by taking the Deutsche Bahn to Berchtesgaden. Just ask a DB employee or call their offices for further information.