Advertised as one of the largest cave systems in Switzerland, St. Beatus is a unique experience, a…read morebreak from the blue lakes and green hills. Just so others don't get bamboozled like me, just be aware that there is an intense hill to walk up, just to get to the entrance. Our group was not prepared at all and being in the middle of the summer, everyone was sweating by the time we got to the top.
It doesn't seem like there's much parking and the caves are a popular tourist attraction. We took the bus from Interlaken for free with the guest cards and I would say it's the least amount of hassle since you don't have to fight for parking. Sit or stand on the right side of the bus on the way back to Interlaken for views of the lake.
You can buy tickets online but if you're staying in Interlaken, wait until you get your free guest card before buying tickets in-person for some discounts. Unfortunately, there are no discounts with the Half Fare or Swiss Pass. There were two places that I could tell that sold tickets on-site. One was a gift shop halfway up the hill and the other was right at the top.
Once inside the caves, the temperature drastically drops. I saw some people in thicker jackets but it was such a cool relief from hiking up and I never felt like it was too cold. Wear shoes with decent grip because it can be slippery walking in the caves. Overall, it took about an hour to go in and out. There's a couple of good photo spots and informational boards scattered throughout the path.
When we were done with the cave, we stayed for a bit at the restaurant to enjoy the views and some refreshments. For starters, it sits on top of a beautiful waterfall and you can see the beautiful, blue waters of Lake Thun.