Designer Nathaniel Chapman has kicked up a new developer blog discussing the overland map in the upcoming Neverwinter Nights 2 expansion Storm of Zehir.
We knew we wanted exploration to be a focus of the game, so in our first prototype of what would eventually become our Overland Map system, we had something that was a little bit more like that Indiana Jones experience. You could walk around the Overland Map and discover hidden locations. Random encounters would actually spawn on the map and chase you down. Different types of terrain slowed you down, too. It really felt like you were travelling these massive distances, exploring the space between all of the interesting locations you'd normally visit in an RPG.
In reality, though, the Overland Map was just a scaled down version of the basic game. There was a lot of very tricky scripting being done to make it work and look right - but at its core the Overland Map used all the logic and code that already existed to make the normal game run. This meant that the encounters running around the map were actually creatures - with their own conversations and AI routines and everything. The more we played around with the prototype, the more we realized that this held the opportunity to be a much more dynamic and reactive interstitial space than in any other D&D RPG that's come before.