They're both very pretty lakes, but imo Brienz is the lovelier, especially if the weather is not so good. Brienz is a gprgeous green, and is even attractive in the rain; Thun is a vivid blue in the sunshine, but not so attractive in rain.

In 2026, choosing between Lake Thun and Lake Brienz depends on whether you prefer "culture and castles" or "raw natural beauty." Lake Thun (Thunersee) is generally considered "better" for those who enjoy historic towns, medieval castles (like Oberhofen and Spiez), and a more "developed" feel with vineyards and sunny lakeside promenades. It is larger and offers more variety in terms of dining and shopping in the town of Thun itself. Lake Brienz (Brienzersee), on the other hand, is the winner for nature lovers; its water has a stunning, ethereal turquoise-green hue caused by glacial particles. It feels wilder, with dramatic cliffs and the famous Giessbach Falls. Brienz is also famous for its woodcarving tradition and the Brienz Rothorn steam cog railway. If you have a Swiss Travel Pass in 2026, you don't have to choose; both lake cruises are free, and you can easily do Lake Thun in the morning and Lake Brienz in the afternoon, using Interlaken as your transit hub between the two.