Springs are natural openings in the ground through which water beneath the surface discharges into hydrologic features such as lakes, rivers, or the ocean. The beautiful springs and spring rivers are among Florida's most valued natural resources; their gemlike refreshing waters have been a focal point of life from prehistoric times to the present (2008). The steady flow of freshwater at a nearly constant water temperature attracted animals now long absent from Florida's landscape. Fossil remains and human artifacts, discovered by divers from many spring runs, attest to the importance of springs to the State's earliest inhabitants. Explorers of Florida, from Ponce de Leon to John and William Bartram and others, often mentioned the springs that were scattered across central and northern Florida. As colonists and settlers began to inhabit Florida, springs continued to be the focus of human activity, becoming sites of missions, towns, and steamboat landings.