This is the 12037th most frequent Russian word.
знаменитый
Famous.
Here, "знаменитый" is used as an adjective modifying "артист", indicating that the artist is well-known.
Этот артист действительно знаменитый.
This artist is really famous.
In this sentence, "знаменитые" is the plural form of the adjective "знаменитый", modifying "музеи" to denote that the museums are celebrated or well-known.
Она посетила знаменитые музеи города.
She visited the famous museums of the city.
Here, "знаменитый" describes "случай" to express that the event is recognized or notable.