A climbing gym dedicated exclusively to bouldering, Ostbloc is a great place in Berlin to practice…read moreclimbing technique. The problems are graded in some modified version of Fontainebleau (i.e. color-coded), which allows for less nuanced differentiation than the V scale. My personal interpretation of the grading system is as follows...
Yellow- Similar to a VB grading. I would describe these problems as ladders.
Blue- Maybe V0 to V1. Some technique for footwork and weight-shifting is useful if you'd like to climb with grace and as little strength as possible, but not necessary if your goal is just to finish. All the holds are huge, and I've seen some people use brute strength to finish these types of problems. There is also some volume climbing and top-out climbing here too.
Green- Approximately V2 to V3. This is where the funs begins. Some are warmup routes. For others, the handholds get crimpy and smaller footholds require precision and balance. The variety of problems provide lots of technical practice. Even some problems with dyno moves!
Red- V4 to V5. Very difficult. Expect to spend lots of time here.
Grey and Black- There's supposed to be some differentiation between these, but I would lump them all as "Is it possible to climb these?!" Disclosure: I'm too intimidated to actually try.
A single day pass is €10, and the 11er card for €100 looks like a decent deal. If I lived closer, the half year or annual subscriptions would be completely worth it.
P.S. Lock rentals require a deposit of €5.