Just 20 miles from Belfast (Northern Ireland / UK) there is a legendary Lake called Lough Neagh. Legends say that it was formed when giant Fionn mac Cumhaill took a large chunk of ground and throw it in direction of the other giant (somewhere in Scotland). He missed and there were two results - the largest lake in Ireland and Isle of Man. The other story tells that the lake comes from an ancient horses urine...
Nowadays giant's are gone and Lough Neagh is not only a tourist attraction but also the major supply of water in the region. It is located in colourful Antrim Town, just 5 miles from Belfast International Airport. Good place for a trip with the family, a date (there is a very nice coffee shop in the Antrim Marina) or just as part of the trip across Northern Ireland. There is another, very famous attraction just within the walking distance - Antrim Castle Gardens.