You've got earth, fire and air. Now the only classical element that's missing from your outdoor living space is water. Whereas fire brings warmth to an outdoor space, water can provide a soothing sound and a dimension of cool tranquility. Water features can of course take all different forms, from small store-bought fountains to cascading waterfalls, it all depends how wet and wild you want to make it.
Koi ponds -- small garden ponds filled with colorful carp -- have become very popular in landscape design because the fish have the ability to transform almost any setting into an exotic, Eastern garden. Koi ponds are best kept in mild climates, because if the pond freezes over for more than a few days, the fish will suffocate. For a less expensive and labor-intensive water feature, many hardware stores and nurseries sell small and medium-size fountains that can be mounted on a wall or perched on a pedestal.