The brain ventricle located in the diencephalon is the ventricle.

Explanation:

Brain Ventricles:

Ventricle system consists of "2 lateral ventricles", "the third ventricle", "the cerebral aqueduct", and the "fourth ventricle".

diencephalon:

sorry to break it to ya but no one can answer your question it's just

jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.