The capital of Northern Ireland, Belfast, is daily receiving thousands of tourists coming in from Dublin on day trips. It is easy to get here using Irish Rail, or by traveling with one of the many buses traveling between Dublin and Belfast daily. It is also possible to join in on organized tours, and if you want an efficient day with lots of experiences and things to see, the Giants Causeway-tours might be exactly what you are looking for!
Belfast is the largest city in Northern Ireland, and it is the second largest on the island of Ireland. The inner parts of Belfast has a population of around 250,000 people, and it has throughout history been known for its linen and tobacco industry and also for shipbuilding. In fact, the Titanic was built here, and visitors who go to Belfast today should absolutely visit the Titanic Museum which might be the highlight above all other highlights in Belfast today.
In addition, Belfast has a very nice city center where you can walk around, do some shopping and see some nice buildings. It is worth noticing that in Belfast the currency is British Pounds (Sterling), so you might want to pay with card or change some money before arriving.
For more information about Belfast, visit the Belfast Guide.