Observatory
Observatory , noun
[Compare French observatoire.]
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.
(Military) 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. — Farrow