A construction block 1, which can be used to build ornamental structures, wall boards, decorative coatings etc., includes a front face 2, a back face 3 and edges 4. Each edge has a projection 5 and a recess 6. The projection includes a claw 7 on both sides of the projection 5, and the recess includes a notch 8 on both sides of the recess 6. The projection matches with the recess in order to connect the construction block 1 to a similar construction block. The construction block includes also a wheel 9 that has wedges 11 for each edge 4 of the construction block. The wedge 11 locks the connection between the construction block 1 and the similar construction lock when turning the wheel 9.