Abstract: The invention is about a modular foldable brick that enables architectural elements such as stacked walls, arches, corners, doors, windows and wall niches to be constructed at indoor and outdoor conditions that divides, restricts and secures a certain space; Due to the possibility of folding the storing and carrying of this brick is possible at a minimum weight. The brick is connectable within itself and also attachable to others for constructing architectural elements as wall building systems. The foldable brick provides a foldable brick body that forms the outer walls and an inner wall being formed with three techniques; connecting/fixing (A-B groups)/encircling (C group). All three techniques are related to the forming of the detachable wall building system's entity unit foldable and sustainable brick. All these three techniques are used simultaneously.