following is a technique i've been taught for making large dios. I don't know whether this is a common method or if any of you guys use it. It is a good technique for making mountains, hills, valleys etc., probably for large dios or large scale dios. you will need
screen (like pool patio screen), newspapers, a staple gun and wall plaster like what you can get at hardware stores.
To make the hill crumple up the newspaper tightly, put it on the dio base and kind of mold it into the shape and hight you want it. You will cut the pool screen to the aproximate size and use the staple gun to staple it to the base over the newspaper. Before you staple it all down, put more newspaper as needed to fill in the spaces and make the shape you want. Staple it all down making sure it is tight. you can create adittional flat areas, ditches, trenches, etc. into the hill by adding a staple to that area. Cover it with the plaster and use the plaster to make it more realistic. Surface as nessassary for your model.
I hope this helps anybody and i hope my directions were clear enough. I'll post some pictures as soon as i fugure out how to. Ask me any questions you have.
---Sawyer