A retaining wall with a series of differently sized, pre-formed blocks. Each block includes a projection and a recess, with the projection and recess arranged and configured so that each projection effectively engages a recess in an adjacent course to connect and align adjacent courses in registry. Retaining walls made of horizontal blocks may be stacked in columnar fashion or running bond fashion. The location of the indexing surface on a projection relative to the viewable surface of the block may be varied to enable adjacent courses to be coplanar or tiered in a variety of predetermined offset distances.