The university I attend holds various different lectures in the university chapel (I am assuming the reason is that it is a big room.) Is it a prohibition to attend the lectures that are held there?
Using the university chapel will depend on the nature of the chapel. If it is meant to be a Catholic place of worship, then you should not go in here even for other reasons. However if it is meant to just be a room for anyone that wants to pray etc. then it isn’t meant to be place of avoda zara, and you may go in there.
Shach Y:D 149-1, Chochmas Odom 64-16, Shearim Hamitzuyim B’halacha 167-6, Igros Moshe Y:D 3-129(6).