I was listening to a Hajj cassette, and it mentioned that if anyone is allowed inside the Kaba one should not look at the ceiling. Why not?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

We are not aware of any evidence which prohibits a person from looking at the ceiling of the Ka’bah when he is inside it.

In principle, this is permissible unless there is evidence which prohibits it.

Allah knows best.