Do you have more of an idea other than just ancient castles?
Answer:
kleptomania is the answer
A dependent clause adds something to a sentence but cannot be a standalone sentence, hence "dependent." In this sentence, "when I had... phone" is a dependent clause.
It is best when drafting to proofread. I am very bad at this so I need to work on it. It is important because you need to check which sentences don't belong or what words have too many silent e's.