We do have plenty of garden space here, but when we lived in an apartment, we were introduced to Earthboxes. Being frugal, we made our own. Here is how....but first, the what and the why.
One of the problems with container gardens is the need to keep the plants well watered. Many vegetables, notably tomatoes, need a steady supply of water and should not be allowed to dry out. This type of container solves this problem by having a well full of water at the bottom of the container, and a soil "wick" to draw the water up to the plant's roots.
The above pail has four inches of water at the bottom, with the soil suspended above it. The trick is to keep the soil out of the water, but to still wick the water up into the soil. The other trick is to keep the pail from over-filling with water, making a swampy pail suitable only for growing cattails. Here is how it is done.