observatory vs observation tower

observatory and observation tower both are nouns.

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

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

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

Other synonyms of observatory include lookout, lookout station.

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