Observatory /(?)/

pl. Observatories

1. A place or building for making observations on the heavenly bodies.

   The new observatory in Greenwich Park.

2. A building fitted with instruments for making systematic observations of any particular class or series of natural phenomena.
3. A place, as an elevated chamber, from which a view may be observed or commanded.
4. A lookout on a flank of a battery whence an officer can note the range and effect of the fire; usually referred to as an observation post. (Mil.)