Is it possible to find a day trip Dublin to Belfast including black taxi tour, C.S. Lewis Square (or is there a better C.S. Lewis site?), Titanic?
You could do this yourself but it would be a very long day. The train from Dublin Connolly Station to Belfast takes about 2.5 hours.
My friend and I did this back in April. We took an early train from Dublin to Belfast and then did the HOHO bus route, getting off at the Titanic Belfast Experience. We spent almost four hours there and then took the train, getting back in Dublin about 9:00 p.m. It was a long day but I am glad that we did it. The weather was miserable but since we had pre-booked the HOHO bus, Titanic Experience and the train tickets several weeks before our trip started, we still went.