Okay, I have been playing since December, but just today started getting notifications saying: "You have just been attacked in the monster arena. Go battle now!" Did I miss something, or is this a new thing?

So, my husband said he thinks it is the pvp, but I have no missed battles in there. Can anyone tell me what this is?

@PoshMrsMoss it used to be for pvp but its no longer you can use it as decoration now

@Marianne-van-Es thats not what she ment. She is talking about the notification people get when not in-game.
You are talking about the building. 2 different things.
I also thought it was pvp, but i get it way too often to be that. No clue what it is now...

sorry thought you ment the building, If your shield is down and tou are attacked you get this notification, I think its to let you know you have a new attack in your defense list and it keeps on popping until... its like the new chest notification as long you dont open it it will pop up