The hydro dam is a power plant building in SimCity 2000. They are relatively cheap to build and are a solid source of power while producing no pollution at all. However, they can only be placed at waterfalls and produce little power per dam and thus require a large amount of money when bought in bulk. As they are one of only two plants not to disintegrate after 50 years (the other being wind turbines) they are a good investment for people who have the money to buy a multitude of them.