What kind of ground cover is good for under swing set?

I want to put some ground cover under our swing set. I've heard that rubber mulch is good, but pricey. Any other ideas? What kind of mulch works best.|||play sand. it's cheap enuff and soft enuff.you may have to clean some out of the grass with a water hose but that's it.You'll be hitting rubber mulch all over the yard mowing.|||You could do creeping thyme. It's cheap!! It's a quick spreader and it handles foot traffic!! It also would provide a cushion to anyone who might trip and fall and land on it!!





Not to mention...when it gets stepped on...it's very aromatic and smells really good!!





Hint hint! whooly thyme doesn't flower so less bees!!





http://www.humeseeds.com/efcthym.htm|||We laid down plastic film then covered with play sand. We outlined the area with railroad ties.|||it depends, if it rains alot, then wood shavings or bark mulch. if it doesn't rain alot, then sand|||They have a new mulch made of rubber...it looks like wood. It might be softer and less messy.