To get to Belfast by car, take the M1 from Dublin or the A1 from Newry. For those coming from the west, take the M2 from Derry/Londonderry.
If travelling by rail, there are regular services from Dublin to Belfast on the Enterprise train. There are also trains from Bangor, Coleraine, and Derry/Londonderry.
If you are in the nearby town of Lisburn, you can take the train or bus to Belfast. If you're visiting the Giant's Causeway, consider taking a scenic rail journey to Belfast afterwards.
The closest airport to Belfast is Belfast International Airport, which is approximately 30 miles away from the town center. The suggested route from the airport to Belfast is to take the M2 motorway towards the city. The journey should take around 30-40 minutes, depending on traffic.