First off, hey all! I haven't been around for a few years but I recently got back into Minecraft and started a survival game. I found this really cool ravine inside a cave system near my spawn point so I decided to build my house into the cave and focus on exploring the ravine. During my exploration I ran across another ravine below the first one and the two were connected by a cave system. I have since decided to build an underground city throughout these two ravines and I need ideas. My current plan, at least for the first ravine, is to just build cliff dwellings into the sides of the ravine and then populate them with villagers (I'll have to go into creative mode to accomplish this). I plan on turning the cave system that connects the two ravines into a giant grand library, I'll need ideas for that too. I'll post screenshots tomorrow, any ideas or advice you guys can give me would be much appreciated!
Why would you need to go into creative to accomplish anything? It's would be easier, but most things are possible in survival. For example trap some zombie villagers and cure them to start your village. That aside, don't forget that a village needs light within 5 blocks of the outside of each door to count as a house. So if your ravine is 11 blocks wide, if you put a row of skylights down the middle of the ravine and the doors are right on the edge they would be valid doors. You might then have to create walkways extending out into the ravine along the edges. Villages get kind of crazy once you start getting more vertical with them so be sure to add in safety rails and keep some villagers locked in a safe room to repopulate in case of a zombie invasion.
I have successfully started villages the way Rodabon describes. The tricky part is keeping them contained so they don't kill the other villager you healed. My solution was to build a long (7 blocks or so) building with doors on either side. Have the zombie follow you in one door while you run out the 2nd door that has a pressure plate on the outside of the building (that way you don't have to stop and close it), then run around to the other side and manually close that door. Then I either put a hole in top or the side to throw the potion and apple at him. I'm sure there are many similar types of methods. I guess you could use creative, but doing it in survival is just so much more fun then tossing a spawn egg at the ground.
I've thought of building something like Moria under an extreme hills biome.
Thanks everyone for the suggestions! What I've done for the first ravine is continue with my cave dwelling plan but significantly expanded to include 3 levels, a town hall, garden, town square, farm, and eventually a brewery. As for the Grand Library, I've scaled it down to include a prison, school, and a triumphal statue symbolizing Minecraft (I'm thinking a pickaxe, paintbrush, and sword). For the second ravine I am going to use DuhDerp's idea of a suspended village. I've also discovered a third ravine that I plan on building a rail line to at some point.