Talk to me!

Our backyard is one giant hill.. so you walk out, there is a small yard that spans the entire back of the house but ends at about 20 feet away from the house, then goes up into a big hill with trees, boulders, you name it. It goes back quite a bit (we're on an acre and the house is smack in the middle of the lot) and I'd love to do something in the future to make this yard space useable... ideas? I don't even know what to google about it!