Even if you think your Zen garden is the ultimate in relaxation, if it doesn't have a water feature, you aren't quite finished. You have a several options here, from tabletop fountains you can purchase in a store or online, to a full-sized waterfall or koi pond. Incorporating a waterfall into a pond is another traditional way to get the best of both worlds. You can spend some money having a water feature installed, or you can save some money and try to do it yourself. There are all kinds of DIY pond kits available online and in your local garden center. These generally require a lot of digging, the installation of a rubber skirt and a recalculating pump to make everything work. The edges of the rubber skirt are then cleverly covered up with plants and rocks. Building or buying a water feature is well worth the investment if you're looking for maximum tranquility.