The in-game description describes it as the "Yafaem Saltmoor," and looking at the map of Eorzea in-game, I came to the conclusion that the most likely place is northeast of Sharlayan, on or near the northern coast. However, I remember reading in the cutscene about how it was along Abalathia's Spine, which implies it's more north/northeast of Ishgard, which would put it more east of Sharlayan instead of northeast.

But I haven't heard anything about this "Yafaem" area prior to this. Maybe I'm just not paying attention, but is there some other place that would fit the bill?