A block for construction of foundation systems retaining walls and gabions and to methods to build walls or gabions from said block. The block is comprised by at least two sides or faces of rectangular and flat configuration (1 and 2); at least one side or face (3) which has at least one of the ends in convex form; at least two sides or faces (4 and 5) which have at least one of its ends in convex form and that together with the convex end of the side or face (3) can provide said block with an apex (6) and respective geodynamic form. The present block is intended for the civil construction sector, more specifically for the construction of retaining walls by means of blocks or applying formwork with the form of the blocks.