Flat gardens, or Hira-niwa, are constructed without hills or water; the flat ground level symbolizes water. In fact, the ground is usually covered with pebbles, raked in circles and straight lines to give the impression of ripples. These gardens contain stones, trees, stone lanterns and wells and are representative of the seaside or of grand lakes. Carefully selected and placed groups of stones symbolize islands; sometimes a waterfall is suggested by upright oblong stones.

Hira-niwa reached their height of popularity during the Edo period, as described in history of Japanese gardens, and are most often found in Buddhist temples as objects of contemplation. The most austere contain only stones, carefully laid out to look pleasing but also to facilitate contemplation. The garden design is very subtle; stone placement oftentimes suggests far off lands and mystical locales.

Many modern flat gardens also contain wells and stone lanterns. The wells usually have a purpose in these gardens: purification of those who wish to observe the gardens. They are typically constructed with wood, and have either a pulley system or a large spoon for drawing out the water. Stone lanterns are not only ornamental, but serve to illuminate the gardens at night.