Both students and teachers spend, on average, far more time preparing for classes and exams than actually together in the classroom. As new university teachers, it makes sense to ask ourselves, how we can put this limited amount of time in the classroom to its optimal use or to put the question differently: what is the optimal value of the classroom in the learning process? In this short essay I will argue that students get most from the classroom experience if we use it for interpreting facts already familiar to the students instead of teaching completely new facts. For this to be possible, the students must have already been previously exposed to the subject, which requires independent work on their part before, and not only after the class. Preparation before a learning unit creates a basic roadmap of the material to be covered and allows one to focus on the more difficult parts. The classroom interpretation then adds to it by enriching the basic facts with personal experience and, sometimes, twists and turns the students would not have expected. This can happen more interactively in a smaller setting, but also one-way in a bigger class. In both cases, the class will help the students to build upon some existing notions, to rethink already learned facts, to put things into perspective, or at least consolidate knowledge. At the same time, it will make the classroom experience more valuable and interesting to students and motivate them for class without enforcing compulsory attendance. In contrast to most other contributors in this volume, I teach engineering and natural science classes, not political science. The following observations on the classroom, however, should be general enough to apply to any subject domain. To motivate them, let us first look at a possible and perhaps familiar classroom experience.