Thought of a possibility that might seem a bit unlikely at first glance; the Orkney Islands. Yes, they're isolated and cold and don't meet most of the other criteria that the OTL cradles of civilization did but it is a fact that five thousand or so years ago the climate was warmer and that there was quite a lot going on in that part of the world, including what could be considered a small scale proto-civilization at Skara Brae and the Ness of Brodgar (the two sites neighbour each other and were in use during the same time period) along with other sites in the area. The problem is that in OTL they didn't really have enough time to develop further than they did before a changing climate forced the inhabitants to relocate. But if things had gone a little differently; if they'd started developing a little earlier, if they'd had crops better suited to the climate than the standard Neolithic Western crop package, if whatever caused the climate to change had held off for a few more centuries (I'm aware that the last one verges on being ASB) then they might've had the time they would have needed to cross the line into being a full-blown civilization and possibly for it to have spread far enough to persist even if the sites where everything began had to eventually be abandoned.