In landscape architecture and garden design, a water feature is one or more items from a range of fountains, pools, ponds, cascades, waterfalls, and streams. Before the 18th century they were usually powered by gravity. Since the 18th century, the majority of water features have been powered by pumps. In the past, the power source was sometimes a steam engine, but in modern features it is almost always powered by electricity. There is an increasing range of innovative designs as the market becomes more established and people become more aware of alternate installation methods, such as solar power. The advantages of using solar power include environmental benefits, no electrical lines in the garden, and free energy. Modern water features are typically self-contained, meaning that they do not require water to be plumbed in; rather water is recycled from either a pond or a hidden reservoir, also known as a sump. The sump can either be contained within the water feature, or buried underground, in the case of an outdoor water feature. Water features can be quite a change for the environment giving calm, elegant and yet luxurious looks indoors as well as outdoors irrespective of its design.