The world of Caldera

In my January contribution to the RPG blog carnival, I put forth that maybe a mideval world arranged like the Ancient Greek city states would be interesting. If you go back and read some previous posts, you might have figured out that if my brain latches on to something, it chews on it relentlessly. So...

Almost immediately ideas started spewing forth from the chaotic swirl of grey bumpy stuff in my skull. This is how it actually happened in my head.

Each city state would be located in a huge caldera. There will be a lake in the bottom. The outside slopes of the caldera would be incredibly fertile farmland. Some of the calderas will have notches cut in the sides from where the water escapes the caldera, some will have underground rivers. Of course any DM worth his dice is now asking himself "What caused the calderas in the first place?" I had a brain fart. Took me about an hour of bouncing ideas off the wall before I found something I liked. The calderas are the leftover scars from a war between Earth and Fire Elementals.
Moving on to Gods in the world. I wanted to stay as far away from the standard D&D god model as possible. Each city state would have a patron goddess. All divine entities are female in this world. At the top of the goddess ladder is Gaia. She gave birth to the four Elemental goddesses. It was at this point, I got a little tripped up again. I didn't want the patron goddesses to be as raw as elementals. Now we come to the Ur, the first ones. There are an infinite number of Ur goddesses. This gives the DM and the players the ability to create a goddess for anything.
I still don't know where the idea came from, but I grabbed it and ran with it. The ocean goddess died or was captured during the elemental war, her sister the river goddess is despondent. The consequences of this is that the oceans of this world are teeming with monsters. Ocean travel is not safe or advised. Sea monsters are going to be fun. What if some of the calderas are filled to the top with water? Would monsters live in those? Is there some way the monsters could leave the caldera? Maybe an underground system of rivers. Oooo, an entire Underdark under water! Time to break out Dragon magazine #267. :-) Aquatic Drow?
At this point I remembered a couple of maps I doodled a few weeks earlier.

Now I have 3 continents for the world. With that much open ocean, I'll have plenty of room for undiscovered, secret, and lost islands. (I have since filled in the maps even more than they are here)
AAANNNDDD... While typing up this post, I had a few more ideas.
Aquatic Drow need to be tribal and wild. Sahuagin will be bigger and more savage. The only way to traverse the oceans is in giant armored ships. I'm thinking waterbourne, mechanically inclined dwarves. They hunt the sea monsters and mine Ice diamonds from ice bergs.

Currently I'm still thinking up goddesses and coming up with city state names. I just had to get this out of my head to make room for more.

Happy Gaming!