Giants Causeway is about 50 miles away from Belfast. Take well over an hour to get there and the same again back. All to stand in the ******* rain and look at rock. You'll be surprised at how quickly that gets boring. Belfast, for the most part, is a hole. Just like any other major city in the UK without anything of architectural or historical significance. You could visit the shipyards to see where they built the biggest boat to ever get ****** by an ice cube, but that's mostly empty buildings and empty docks. There's the terrorist tours that'll take you down the falls and shankill, but they're **** holes and you wouldn't want to stop on them anyway except to take pictures of the murals. The Crown Bar is probably the only redeeming thing about Belfast. The people are horrid unless they're trying to sell you something, the food is mostly asian, the clubs are like any other in western civilisation. Down royal is a racecourse. That's it. **** all else there. Lisburn is near it, but the only thing there that's of an interest is the linen mill and unless you have an interest in collecting dish cloths and bed sheets, is ridiculously boring.
You could go to Derry, the city of culture. But it's even more of a stinking hole than Belfast and with the dissident threat at it's highest in years you'd probably be safer playing with dodgy chinese fireworks over the holiday period you got from Nutts Corner market.