Interlaken's nightlife divides cleanly between the staid hotel bars of the Hoheweg and the rowdy, international backpacker scene around the Ost station. The latter is dominated by the adventure tourism crowd: people who have spent the day jumping off things, flying from mountains, or abseiling into gorges, and who require beer, loud music, and other people in a similar state.
Bar Metro is the best-known venue in this strip, a basement bar that has been the default meeting point for young international travellers for years — cheap by Swiss standards (which is still expensive by most others), open late, and reliably full in summer. Several similar bars operate within a few minutes' walk. The hostel bars along the same stretch also attract non-guests and are worth checking. The scene is unpretentious and welcoming; the clientele is overwhelmingly in their twenties and speaks a dozen languages.