The River Manzanares meets up with Lake Santillana just outside Manzanares el Real. This lake is one of the main water-supplies for the metropolitan area of Madrid. King Alfonso XII put the last stone in the original dam in 1908, almost submerged with only the top of the towers and part of the dock now visible, when the new dam was built in 1969. The fauna is based on fish and the abundant aquatic bird life. Lake Santillana is extremely popular with anglers fishing for the carp and pike as well as the birdwatchers trying to catch a glimpse of the varied bird life.