Similar to a small basement with a patio over the top. Don't forget to leave a manhole for maintenance. Seal inside with Thoroseal so chemicals from the concrete don't leach into water. Hook up to gutters and you have free water. Use a some type of diverter to flush the leaves and bird poop out before water enters cistern. Then you need a pump, pressure tank, foot valve, pvc pipe and you are all set.I'm going to look into this for storage. What is the construction?