Abstract: Retaining wall blocks are disclosed, which are trapezoidal in shape and have a positive interlock. These blocks can be used to construct walls, especially garden walls, that are strong and either straight or serpentine, with concave or convex surfaces. More particularly, the blocks, thanks to their structure, can be used to construct tree rings or wells, patio walls with or without corners, straight walls with curved ends, serpentine feature walls, L-shaped walls, lawn and driveway edgings, small steps, free-form shallow ponds, planter boxes, window wells and the like. Advantageously, they can be produced in the form of units comprising blocks of the same or different type, e.g. of the stacking, coping or corner type, which can be assembled in the form of very light bundles easy to store and transport.