A concrete building block (30) includes a body (32) having opposite first (34) and second sides (36), opposite first (38) and second end faces (40) extending between the first and second sides (34, 36), and opposite first (42) and second bearing faces (44) extending between the first and second sides (34, 36) and the first and second end faces (38, 40). The first side has a first section (52) and second section (54). The first section (52) and first end face (38) are shaped to mate with each other when a like block (30) is rotated 90° and oriented adjacent thereto so that the center plane for the two blocks (30) are perpendicular to each other; and the second section (54) and second end face (40) are shaped to mate with each other when a like block (30) is rotated 90° and oriented adjacent thereto so that the center plane for the two blocks (30) are perpendicular to each other. The building block (30) can be used for structures such as a free standing wall, retaining wall, garden wall, or columns.