Build a Sandbox
You're landlocked, so what. Take the kids to the backyard beach. Here's a how-to on building your own sandbox. Location is a key consideration when planning your sandbox - partial shade is nice but beware of digging near trees and damaging roots. Lowes recommends using cedar as it's waterproof and less likely to splinter.
Throw in a pail and shovel and maybe even a plastic pool and you've got a urban (or suburban) paradise.
