Harder Kulm is the closest mountain of note to Interlaken, and its popularity reflects that proximity. The summit, which boasts a well-reviewed eatery and beer hall (the imposing Panorama Restaurant), also has live Alpine folk music every Saturday from late May through late October.
It’s arguably the most enjoyable point to view the Brienz and Thul, the massive lakes on either side of Interlaken. At sunset, the view of the high peaks aglow in the dying light of the sun is a sight to behold. Expect to pay 30 CHF for a round-trip ticket from Interlaken.