Hello Rosie,
I'm pretty sure that you're younger than most members on this site. That's great, but it does mean that we assume things (like knowing the tunnel entrances, their names and map co-ordinates.) To get a question like "please tell me about Kitt Hill" is a bit like asking why some things break if you drop them but some don't. What I mean is "it's a bit more complicated than that".
If you follow the links given by Morlock and ICLOK you should get what you need. If you need more, get back to us.
🙂 John
sleep is a caffeine deficiency.