The City of Estuary, Pearl of the Northern Coast, is located at the mouth of the Giant's Arm river, which reaches most of the way across the continent of Iburia. As such, Estuary is a major trading hub, and center of culture. It is well known that one can find nearly anything in Estuary, be it goods, beasts, people or knowledge.
In real life:
Estuary is a gaming materials website created by Arazyr, primarily as an outlet for some of the Open Game Content he has created over the last few years. The City of Estuary was the first city Arazyr thought up for his homebrew campaign setting, so it was a natural choice to use as a framework for the website.