Venitian Pool
In the early 1900's, a developer,
Mr. Merrick, was mining for linestone and hit the Biscayne aquifer.  Since then, this rock quarry has been developed into a public swimming pool for Miami-Dade county.
Spring water used to be pumped and drained into the spring monthly, but this proved to damaging to the aquifer. 
Venetian Pools has since recycled the spring water to limit the pumping of it from the aquifer.  There was a slight chlorine smell when visited in 2004.