Dam

Dams generally serve the primary purpose of retaining water or prevent water flow into specific land regions. But dams are not completely waterproof structures. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to provide generate electricity. Infact stored water could be released through turbines to a generator. To boost the power generation capabilities of a dam, the water may be run through a large pipe called a penstock before the turbine.
During an armed conflict, a dam is to be considered as an "installation containing dangerous forces" and shall not be made the object of attack.

@B Do you know Three Gorges Dam?

@ More about Pumped storage hydroelectricity