Living in the middle of the city where many people don't even have a yard, it's fairly rare to have a nice garden. We are lucky enough to have a little bit of a back space... but unfortunately our landlord decided to cover it with asphalt years ago. When we first moved in we had a raised bed (made out of an old wooden box used to ship artwork up on cinder blocks). But as it was crappy wood and we live in a wet climate, after a few seasons, it was pretty much dead So I asked my landlord if I could tear up some of the asphalt and install a permanent redwood garden box... to my surprise she said yes.
Using a busted chisel, a hammer and an old climbing axe we chipped out a 6x8' block of asphalt. We made a box out of nice redwood with legs to anchor it in place (having it recessed below the asphalt keeps the dirt from "escaping). A neighbor was excivating their backyard (which hadn't been touched in over 20 years) so we took a bunch of their dirt, mixed it with compost and potting soil and now have our own flourishing garden box.