Abstract: A barrier block for defences protecting coastal and riverside structures, aracterized in that it is constituted by a central core (1) of substantially cubic shape having firstly top and bottom faces (12) provided with respective top and bottom anvil-shaped legs (2), the anvil-shaped legs having respective top and bottom surfaces (20) disposed parallel to one another and to said top and bottom faces of the core, the anvil-shaped legs further including inclined flats (22) stemming from opposite unhidden side faces (11) of the core; the core having secondly opposite front and back faces (13) provided with respective front and back legs (3) in the form of four-sided truncated pyramid, one pair (31) of opposite sides of the pyramid-shaped legs stemming from the sides (21) of the anvil-shaped legs and the other pair of opposite sides (32) having their bases at least partially in common with one edge of the adjoining un-hidden side faces of the core.