One boundary of the Illawarra is not in doubt - because it is hard to argue with the Pacific Ocean.
And the Royal National Park is hardly a grey area, so let's say the northern border is settled.
But to the south, and to the west, an attempt to nail down where the Illawarra starts and finishes runs into a perfect storm of statistics and politics.
It's fair to say most residents believe the Illawarra stretches south from Helensburgh, bounded by the ocean to the east and the escarpment in the west.
But the argument was ignited recently when Shoalhaven and Wingecarribee council areas were given access to money from the lease of Port Kembla port that was promised to the Illawarra region.
Illawarra Regional Information Service executive director Simon Pomfret sticks to the definition he has always used - the Australian Bureau of Statistics' official definition of the Illawarra Statistical Division. This includes the local government areas of Wollongong, Shellharbour, Kiama, Wingecarribee and Shoalhaven.
But Wollongong Lord Mayor Gordon Bradbery believes "Illawarra" is clearly Wollongong, Shellharbour and Kiama - and said fudging this definition had cost the region funding.
"We are a very succinct entity and clearly defined by geographical features," he said.
"It's an escape route for politicians and bureaucrats to say that we're linked in with others.
"Bureaucracy in NSW is all over the place in terms of where the boundaries are."
Shoalhaven Mayor Joanna Gash said her personal opinion was for the smaller boundary.
"I was always very parochial about the fact that I felt that Shoalhaven City was capable of being on its own, and was never really recognised as part of the Illawarra ... except for funding purposes it always seemed to end at Kiama," she said.
The NSW Department of Local Government includes all five LGAs in its definition of the Illawarra - including Wingecarribee and Shoalhaven. Wikipedia agrees.
But the NSW Planning Department's Illawarra Regional Strategy has just Wollongong, Shellharbour and Kiama.
For certainty the Mercury looked up the Geographical Names Board, where we could search for "Illawarra" under place names. But there is no such place to be found. Lake Illawarra is the closest.
Wingecarribee Mayor Juliet Arkwright said there was a difference between the "geographical-emotional" lines people drew, and government boundaries, as far as her area was concerned.
"There is a folk, or cultural identity that says it's the Southern Highlands - that doesn't necessarily mean much in terms of governance or bureaucracy," she said.
If any part of the Southern Highlands could sneak into the Illawarra, it would be Robertson, sitting at the top of Macquarie Pass. But Robertson Pie Shop owner Will Bleeker is pretty sure where he stands.
"I always assumed that the Illawarra was the part down the bottom [of the escarpment]," he said.
"I thought we were the Southern Highlands."
Robertson potato farmer Warwick Hill agrees that the escarpment is the regional boundary.
"It seems to be that's the opinion of everyone," he said.
Destination Wollongong's Mark Sleigh is also happy to use the more narrow definition.
"From a tourism reporting perspective, Destination NSW defines the Illawarra sub-region as being made up of the Wollongong, Shellharbour and Kiama LGAs," he said.
"Destination Wollongong believes that a strong, united brand for both the Illawarra and South Coast are essential to driving the visitor economy."
The last word should go to the region'a chief statistician, Mr Pomfret: "I don't think it will ever be solved," he said. "In terms of statistics and politics, it's a good combination."