Do raised gardens have bottoms?

Im considering adding a couple small raised beds to my awkward space on my back patio. I have sprayed grass/weed killers and am nervous that even with a raised bed it may be dangerous for us to eat the fruits or veggies planted. Im adding a link to a pic of my "awkward space"...other than a raised garden I dont know wha to do with it! Any crafty ideas are very welcome!! *the swingset is not going to be there* a href="http://www.facebook.com/#!/photo.php?fbid=10150247914808087&set=a.10150207860888087.304524.587023086&type=1&theater" rel="nofollow"http://www.facebook.com/#!/photo.php?fbi…/a