Exclamation mark !!!

Yeah, on my white castle, an exclamation mark , must be a bug right?

I'm experiencing the same issue, there's an exclamation mark sprite over the castle as if the white castle on my home island was a bandit leader camp :P

I've seen exclamation marks on adventures now also..

I have this same glitch on my white castle , I have an exclamation mark with a gold crown in a circle over mine but cant find any reason in the forums as to why it is there.
Anyone have an answer yet?

That exclamation mark with the crown means it is a leader camp.
The White Castle is a leader camp in the adventure "Stealing from the Rich".
Obviously the same graphic (including the exclamation mark) is used for the reward you can build yourself.

Ahh , thats a tad annoying.
Cheers