about 15 miles
Depends on where abouts in Northern Ireland.Shortest distant from Northern Ireland to London is from Kilard point, County Down (bottom of Strangford Lough) is 293miles.Longest distants is from...
About 93 million miles.
Belfast is in northern ireland
6,022.89 kilometres (3,742.46 miles)
I do not know what the oldest castle is in Northern Ireland.