* "Its" is a possessive pronoun: It shows that something belongs to something else. For example, "The dog wagged its tail."
* In this sentence, "its" should be replaced with a possessive noun: We need to specify *what* is famous for its glass.
Here are some corrected options:
* Venice is world famous for its glassblowing. (Here, "its" refers to Venice)
* Venice is world famous for the glass it produces. (Here, "the glass" is the object)
* Venice is world famous for its beautiful glass art. (Again, "its" refers to Venice)
In short, "its" needs a noun that it can modify to make the sentence grammatically correct and meaningful.