Radionica Architekture has designed their proposal for the Collider Activity Center in suburban Sofia. The proposal won one of five first place prizes and is a “small artificial mountain”. The entire facade opens for nice weather and the internal space becomes a part of the exterior. The building is almost “breathing” with its multi-layered facade that acts as a kind of organism. The hallway exists between the first and second layer of the exterior. The building is meant to be “climbed constantly”. The roof is an umbrella roof that can be opened or closed depending on the weather. The structure’s “three basic layers are open in front of us like when you are peeling off an onion”.