content: It is an evaporative cooling tower. Hot water is injected into the tower (usually around mid height) and evaporates as it mixes with the air.  The process of evaporation cools the wate  ff8  r (that which doesn't evaporate)  and heats the air.  The hot air then rises through the tower sucking in more cool air from around the base and the process continues.   The cooled water collects at the bottom of the tower and is removed via the drain seen in the OPs picture. These towers are typically used by power plants that use steam turbines and need to cool hot waste water (from the condensers) before being released back into the environment.     wiki: Cooling Tower