Nirvana

"Restful" is the most common word used to describe Nirvana, and with good reason. The souls of the plane generally wish to live among other like minded individuals and take in the beautiful sights of this impressive plane. It's the least warlike of any plane (save perhaps the boneyard) and most time is spent relaxing, taking in the view, or exploring.
What sets Nirvana apart, both as a plane and as an afterlife, is that the souls here are rarely striving for anything. Most have worked hard for their mortal lives, and do not wish to do so any longer. The position of the plane within the absurd geography of the outer planes makes it extremely difficult to attack, and the outsiders native to the plane (traditional angels) are much more powerful than their appearances let on, and easily track down and dispatch intruders.