This video explains Tundra Orbits, and the last part of this video shows how to make one in KSP.
Below is a link to KSP
Below is Universe Sandbox
Wiki: http://en.wikipedia.org/wiki/Tundra_orbit (seriously, someone needs to start adding things to it)
👉 I am a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com