Santillana reservoir, also known as Manzanares el Real reservoir, is a body of water along the Manzanares river located in the municipalities of Manzanares el Real and Soto del Real, in the Community of Madrid, in the centre of Spain. It has a maximum surface of 1052 ha, the longest distance between opposites shores reaches 30 kilometres (19 mi), and the total volume of the reservoir is 91 hm³. The first dam was built in 1907, but in 1969 a new and higher dam was built. This new construction was 5 m higher, which allowed the reservoir to have a volume twice as large as before.