Concrete blocks configured for use in forming retaining walls that require the use of rebar and grout to structurally anchor a retaining wall to a foundation. The blocks include first and second core openings extending through the blocks. The core openings are configured so that when the blocks are stacked into courses with other blocks, the core openings of the blocks line up in a manner that allow rebar to extend through the core openings from the foundation to the top of the retaining wall. Further, the core openings facilitate pouring of the grout down through the aligned core openings. In addition, the core openings are configured so that the core openings do not overhang joints between blocks or overhang block edges that would allow grout to leak out as grout is being poured down the core openings.