well

In its commonest use, a well is a vertical shaft that people bore into the saturated zone of substrate in order to draw up groundwater. In literature and old maps, especially of the desert Southwest, Well appears often as a place-name where no wells have been dug, but where naturally occurring springs are reliable enough to be well-known for human use. A splendid example is Montezuma Well in Arizona, where a warm spring emerges from the bedrock and a travertine rim around the spring has created a pool.

Barbara Kingsolver