Since I am relatively new to running my own game, I thought it might be helpful if I jotted down some observations about the world-building process. I have thus far run one session of campaign called The City of the Groaning Gate. The titular city is called Hrulvir, which is an unabashed pastiche of Lankhmar, Sanctuary, and every other city that looms imposingly within the books that I've read throughout the years.
Thus far, I have a huge city lurking behind impenetrable black walls, that sits on the shore of the flint-grey Eastern Sea. The broad, slow-moving Black River snakes past on its western flank and continues to slither languidly across the length of the continent until it eventually empties into the Western Sea
Hrulvir is positioned between the Serpent Spires, a range of mountains that stretch horizontally across the continent, and The Barrier Peaks, a range which form a vertical ridge down the eastern shoreline. North of the Serpent Spires is an icy waste teeming with marauding tribes of subhumans. Far south, the vast Wastes of Ahura bake underneath a cruel sun.
This is really all I have right now. I know that there are several trade towns located along the Black River. There is also a horde of beastly warriors assembling under one banner along the Northern Wastes, known as the Crimson Horde
I am a firm believer in the notion that the setting will create itself as the story unfolds. This has played out during every attempt that I've made to write stories, and I'm hoping that the same holds true when I run this game.