I've created a castle out of a large mountain close to my spawn. Yes, it took a great amount of time. No, I didn't use any inventory editors. I like my mines to be wide open so I get a lot of coal and cobblestone. Combined with my forge, I had plenty of stone to build up these walls. (I don't like cobblestone superstructures, the stone ones look much smoother)

I uploaded images to imgur because I didn't feel like converting them to jpegs in order to upload them here. http://deathsoverture.imgur.com/castle_atreus

Additional Notes

The only mod I used is an Ambiance Occlusion mod