There are three main components of a Zen garden. They are the sand/gravel, the rocks and stones and the plants and trees.
Larger Zen gardens incorporate winding pathways, small buildings and gazebo-type structures throughout. These are meant to give visitors additional things to meditate on.
There is never any water in a Zen garden. Instead, the sand or gravel is raked to form lines that are supposed to represent the ripples and waves in water.
Raking the sand or gravel in a Zen garden is a meditative practice. It takes a good deal of concentration to make perfect lines and curves, so many people find the process calming.
Zen gardens hail from Japan, which still has the most beautiful examples of the gardens in the world. Kyoto has six major Zen gardens, the highest concentration in Japan.