An infinity edge pool (also named negative edge, zero edge, disappearing edge or vanishing edge pool) is a swimming or reflecting pool which produces a visual effect of water extending to the horizon, vanishing, or extending to "infinity". The term also is used to describe (however, incorrectly) perimeter overflow pools (pools that may be on level parcels, wherein the water flows over one or more edges, usually flush with the decking elevation). One type of location in which the effect is particularly impressive is where the infinity edge appears to merge with a larger body of water such as the ocean, with the sky (if the pool is located on the side of a hill or field of green).
Infinity edge pools are often seen at exotic resorts, exclusive estates, and in advertisements. The infinity pool design concept is said to have originated in France, where one of the first vanishing edge designs was utilized in the "Stag Fountain" at the Palace of Versailles in the early 1600s.
Infinity pools are often very expensive and require extensive structural, mechanical (hydraulic engineering) and architectural detailing. Since they are almost always built in precarious locations (cliffs, mountain tops, beach front,etc.), sound structural engineering is paramount. The structural engineering must be based upon the geological conditions found on the site. A geotechnical report is commissioned prior to the commencement of the structural engineering. The high costs of these pools is often found in the foundation systems that anchor them to the hillsides.
In reality the edge of the pool terminates at a weir that is 1/16 - 1/4" lower than the required pool water level. A trough or catch basin is constructed below the weir. The water spills into the catch basin, from where it is then pumped back into the pool.