A war theme
Strolling in Belfast or Londonderry / Derry, you will see dozens of huge wall paintings with one theme: war. In Nationalist neighborhoods, the colors are those of the Republic of Ireland, green white and orange, while in Unionist neighborhoods they are red, white and blue for the UK.
The tension is still very recent, and it's better not to talk to much about it with the locals, ve will often simply avoid answering your questions. Be careful, if you say Londonderry, that means you are a Unionist, and if you say Derry you are a Nationalist ... so the easiest thing to do is just call it "this