A retaining wall block having a front surface, a rear surface, side surfaces, a top surface, and a bottom surface. Each side surface comprises a first section, a second section, a third section, and a fourth section, with the sections configured and arranged to allow a plurality of blocks to be arranged in a convex wall structure. The retaining wall block includes a projection that is configured to abuttingly engage a portion of a vertically adjacent block in a wall structure. Preferably, the block has a width/depth ratio in the range of about 1.87 to 2.67. The retaining wall block may be combined with an earth anchor for use in multi-course walls.