I just started thinking about a sandbox campaign I would like run in a PbP. My GMing experience only extends to running APs, so I feel a little out of my depth. I'm looking for both general sandboxing advice and campaign specifics.
I would like it to be heavily player driven, and possibly more focused on roleplaying than combat. I'm unsure whether I should run it like a large single player campaign, or bring the PCs together. What would be a good location? I would like something urban, but there are so many cities to choose from. Korvosa immediately sprang to mind, but maybe Absalom or Magnimar would work better.