Lake Thun is one of Switzerland's most beautiful lakes, stretching 17 km west of Interlaken. Its emerald-green waters reflect the Alpine peaks and are surrounded by picturesque villages and medieval castles like Spiez Castle and Oberhofen Castle. Historic paddle steamer cruises depart from Interlaken and stop at several charming locations. Public swimming beaches are available in summer, and the water is clean enough to drink. The lake offers kayaking, sailing, and stand-up paddleboarding.