observation tower vs observatory

observation tower and observatory both are nouns.

Word	Noun	Adjective	Verb	Adverb
observation tower	Yes	No	No	No
observatory	Yes	No	No	No

As nouns, observation tower and observatory are synonyms defined as:

observation tower and observatory: a structure commanding a wide view of its surroundings

Other synonyms of observation tower include lookout, lookout station.

observation tower (noun)	observatory (noun)
a structure commanding a wide view of its surroundings	a building designed and equipped to observe astronomical phenomena
	a structure commanding a wide view of its surroundings