What covering is best to put Climbing Frames/Swings on?

[JigBugs]

Just thinking of buying some play equipment for our garden and don't really have grass to put it on. What covering do you recommend - mulch? bark?

How about rubber matting? apparently it is much better to fall on than grass, and won't get thrown about or walked into the house.
I did a google search on 'outdoor rubber play mat'and found lots of links.
Last year I was looking into this for our garden, never got round to ordering any, but I did find plenty of companies who will do them with little cut out shapes, fun colours, etc.