There is so much history here. I highly recommend the Black Taxi Tour & seeing the Titanic Museum. There's also been quite an effort to make Belfast a destination. Shopping, food, & pubs were great. Not nearly as fast-paced as Dublin, which I prefer. If time permits, definitely try to make a day-trip to the Giants Causeway, Carrick-a-Rede rope & Bushmill Distillery. Also, a day trip to Derry is a great idea especially if you enjoy history.