I think if you go to the end of the island you can see three islands that are old Liberty City and if you Zoom in on one of the tall buildings there you could see a sign that says Remember Us? then a sad face. Or the three islands and a bridge halfway through where there trying to connect them if you get 100% the bridge is completed and you can go to portland, stauton, and shoreside vale. Another thing could be that the ghost town is this city and you can find the bank Claude and Catilina robbed.