The answer "In the mosque are small cats." is marked wrong for lacking "there" after mosque. Isn't this already implied by "in the mosque"?
Methinks thine style is a bit obsolete (or poetic). It is better to keep things natural sounding for all intents and purposes in this course.
Your answer should have been accepted, please post your complete answer?
"inside the mosque" would be "caminin içinde" :)