A novel building block is described which is formed of two similar interlocking elements with chamfered surfaces to allow the elements to rest against each other. In one embodiment, the block is used to made structural walls, In another embodiment, a single block with a transparent or translucent pane is provided to form a window. In yet another embodiment, a building is made with at least one floor, one roof and support structures supporting the roof and being formed of the interlocking elements. Each element is made of L-shaped components.