Living in Sunderland, I'm learning to distinguish (just about) the slight difference in accent between the Sunderland folk (Mackems) and the Newcastle folk (Geordies) 10 miles further along the road.
At a bakers shop I call into in Sunderland, the owners wife was complaining, in a broad Geordie/Sunderland accent, about how all the workmen, working on the road outside their shop, were Geordies!!!

I'm originally from Middlesbrough, just 30 miles South, and the Teeside accent has more in common with the Scouse/Liverpool accent over 100 miles away.
The Geordie accent seems to stop very close to Newcastle/Gateshead, still evident in Durham, but very much softened.
I think it's wonderful how we have so many completely different regional accents only a few miles apart but I often imagine how difficult it must be for foreign visitors, who must feel like they're crossing international boundaries every 30 miles!