With a little thought, run-of-the-mill city infrastructure can be reenvisioned for play. I encountered an exquisite example of such creativity on a day trip to Rotterdam: a flood-retention zone with a basketball court in its basin, and seating cut into its walls.

During the rapid urbanization of the 20th century, many cities were designed for the people building them: able-bodied men who weren’t typically caring for children. This created all sorts of lingering obstacles for kids and their caregivers: Think metro platforms reachable only by descending a flight of stairs (not easy with a stroller), or bus ro... See more