Ulster Museum and Botanic Gardens = free!
Tour of City Hall.
Ulster Folk & Transport Museum near Holywood in Cultra.
Ulster Folk & American Park.
Drive up the Causeway Coast to Dunluce Castle, Giants Causeway, Ballycastle and Portrush.
Carrickfergus Castle - unique in the British Isles.
Visit to Tollymore Forest and Newcastle.
Marble Arch Caves near Enniskillen, County Fermanagh.
Giant's Ring near Lisburn.
Navan Fort in Armagh.
Downpatrick for St Patrick's Centre, nearby purported burial site and St Patrick's Way walks.
Helen's Bay.
Visit Tayto factory in Tandragee, Armagh.
If you are a group of ten, book a visit to Coca-Cola factory.
As you can see, I'm NOT recommending anything to do with the Troubles as we're about much more than this still contentious history.
After all, our history does predate the Troubles by a long way!