Closed straight ruled helicoid

Surface generated by the helical movement of a straight line (blue) around an axis (red). The generating line meets the axis (closed helicoid) and is perpendicular to it (right helicoid). This surface is also an example of a surface of minimum area, that is one of the surfaces that can be obtained by immersing a wire (in this case arranged in a helix) in soapy water. It is a non-algebraic surface.