With a total surface of 80 sqm, Chiemsee is Bavaria's biggest lake and is renowned for the good quality of its water. There are kilometer-long beaches all around the lake, with comfortable lawns and many playgrounds.
Also be sure to try out the many small lakes in the surrounding area: Friedlsee, Simssee, Langbürgner and Pelhamer See, Hartsee, Tüttensee, Tinninger See, Stettner See, Klostersee and Alz are well worth a visit.
Chiemsee is also a popular location for sailing and surfing, with usually very good wind conditions. Other possible activities are canoeing and diving. On chilly days, pay a visit to the Prienavera adventure pool or the Bad Endorf spa which includes a large sauna area.
The area also offers many beautiful biking and hiking trails, notably the Chiemgau Alps which offer great views of the lake. If you're feeling adventurous, be sure not to miss the Aschau climbing gardens, take a rafting tour on the Tiroler Ache river, try paragliding or go on a balloon ride.