observatory Location of telescopes and other equipment for astronomical observations. Large optical telescopes are housed in domed buildings, usually sited well away from the smoke of cities. Radio observatories are open sites containing one or more large radio telescopes. The largest radio-telescope dishes have been built in natural mountain hollows: the Arecibo Observatory in Puerto Rico is 300m (975ft) across.

ob·serv·a·to·ry / əbˈzərvəˌtôrē/ • n. (pl. -ries) a room or building housing an astronomical telescope or other scientific equipment for the study of natural phenomena. ∎  a position or building affording an extensive view.

observatory.
1. Building used for observing natural phenomena, usually astronomical, meteorological, etc., using special instruments, telescopes, etc.

2. Building commanding an extensive view, e.g. a belvedere or gazebo.