The present building block has at least one load bearing surface, the load bearing surface of the block having mating interlocking portions comprising cores and protruding interlocks receivable in the cores. The blocks are configured so that each end of a block comprises a half interlock and adjacent ends of a pair of blocks in a course together define an interlock portion that interlocks with a mating full interlock portion carried by a block in an adjacent course of blocks. The basic building block has ends that are oblique such that rows having a preset radius can be formed or such that a linear row can be formed by placing one block front-to-back and an adjacent building block back-to-front. Disclosed are angle blocks with and without splitter wedges, stretcher blocks with and without splitter wedges, blocks for forming corners and posts, cap blocks, and blocks for capping posts.