Add cap blocks to the top row of a block or stone retaining wall. You can add a layer of masonry adhesive to hold them in place, then back fill. Or you can backfill as you go, then add the cap. Either (Patio Step Retaining Wall)
Instead of using stone or timbers, make an attractive, long-lasting retaining wall from pressure-treated plywood and trim boards. Construction is fast and simple, and the materials are much lighter to work with.