Ah, memories
Anyway, I spent a while yesterday exploring in a map with Exoddus at the centre.
Unfortunately it's a bit buggy (those vertical lines) but here it is, with annotations (also, I think a glitch might have destroyed the map immediately after I took the screenshot, so this might be all that remains).
None of the names have to stick, though the Mongo River I think is apt.
The Archipelago of Unusual Geography is mildly interesting, and the mountains above the lava pool are fantastic, well worth a look (their highest point is 4 blocks below the map's upper limit).
Accidental Survival Island is where I spent one interesting night while cartographing.
Dead Splat Island is where I met a creeper (but not for very long).
The Grand Canyon is a mostly open-to-the-sky ravine, somewhere in that forest.
I'm gonna modify the Mongo River a bit to cut it off from the ocean there, and give it a thorough exploration. I don't know what's at either end but I hope to find out. One end goes near the mountains So we could perhaps modify its course and build Ma'Spa there.