On property at any corner formed by intersecting streets, it is unlawful to install, set out, maintain or to allow the installation, setting out or maintenance of any sign, hedge, shrubbery, natural growth or other obstruction to the view, high-er than three feet six inches above the level of the center of the adjacent intersection, within that triangular area between the property line and a diagonal line joining points on the property lines twenty-five (25) feet from the point of their intersection, or in the case of rounded corners, the triangular area between the tangents to the curve and a diagonal line joining points on such tangent twenty-five (25) feet from the point of their intersection. The tangents referred to are those at the beginning and at the end of the curve at the corner. (Prior code § 38.02.022)