In the aftermath.

So a lot of games do New Game+, but what's it called when you beat the game yet it doesn't stop there. I played this game along time ago (late 90's early 2000's) where I beat the main storyline and was surprised at what happened next. I was actually able to keep exploring! This was so fascinating to me to see the world after the story finished. I wish more games utilized this especially the RPG's since that seems like the natural genre for this mode. Does anybody else like this feature or is it just me? also does anybody else know of some good games with this.