observatory

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A building, place, or institution designed and equipped for making observations of astronomical, meteorological, or other natural phenomena.
2. n. A structure overlooking an extensive view.

Century Dictionary and Cyclopedia

1. n. A place or building set apart for, and fitted with instruments for making, observations of natural phenomena: as, an astronomical or a meteorological observatory. An astronomical observatory is so planned as to secure for the instruments the greatest possible stability and freedom from tremors, protection from the weather, and an unobstructed view, together with such arrangements as will otherwise facilitate observations.
2. n. A place of observation at such an altitude as to afford an extensive view, such as a lookout-station, a signaling-station, or a belvedere.

Wiktionary

1. n. A place where stars, planets and other celestial bodies are observed, usually through a telescope.

GNU Webster's 1913

1. n. A place or building for making observations on the heavenly bodies.
2. n. A building fitted with instruments for making systematic observations of any particular class or series of natural phenomena.
3. n. A place, as an elevated chamber, from which a view may be observed or commanded.
4. n. 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.

WordNet 3.0

1. n. a building designed and equipped to observe astronomical phenomena
2. n. a structure commanding a wide view of its surroundings