Mist ONLY around the horizon (cycles) For too long I’ve struggled to get mist to work in Cycles the way it works in the Blender Internal render - that being mist that sits just around the horizon, giving a distant look. To my disappointment, the mist generated in Cycles tends to cover the whole sky giving an overcast look.

How does one achieve a distant horizon where mist only hovers around the horizon?
Cycles Volumetrics are rather slow and for this specific setup, a compositing solution may be more suited, however you can use the geometry information to limit the density of volumetrics.

In this example I created a large cube, encasing the scene, and made the Z information influence the scatter density. That way, the density is high near Z = 0 (the ground) and low as Z grows (the sky).