Architectural building block system

An architectural building block system comprising:

• (a) three side walls, each having an inside surface and an outside surface, said three side walls cooperate to form a triangular tube, said outside surface of each of said three side walls extending from an inner surface to an outer surface and said inside surface of each of said three walls is disposed substantially at right angle to each of said inner surface and said outer surface;
• and
• (b) three channels, each channel disposed on one of said three side walls on said inner surface, wherein said each channel extending from said inside surface to said outside surface of said one of said three side walls, a rebar received by each pair of said three channels and said each channel converges as said each channel extends from said inside surface to said outside surface of said one of said three side walls,
• wherein at least one said side wall is configured to be positionable so as to mate with a side wall of an adjacently disposed block to form two aligned channels to receive said rebar, whereby curved structures are constructible from a plurality of such blocks to form a dihedral angle between each set of two blocks.