We do a lot of work with Plant the Seed, a Nashville based non-profit that specializes in garden education. At one of their garden sites the kids have a small play area, but it regularly pooled with water and made a muddy mess. Our solution was to dig a dry well beneath it! We dug this large hole and filled it with rocks and a layer of gravel, then covered the hole with geo-textile fabric (a water soluble and sturdy fabric for landscaping) and playground mulch. This kept the area soft and kid friendly on the top, but left a large area where water can collect and drain away beneath them.