although I have plenty of space I LOVE growing things upwards..I have arbors everywhere ..and most of them have grapes growing on them..I also use lattice extensively on my property..which also has grapes and privacy vines up them..near them are also
trees, shrubs, perennials, ground covers,
mushrooms, and
root crops..so things are layered..
you can also hang things, but I hate hauling
water to hanging baskets so I don't.
and yes you can do things like layering
chickens ..to heat a greenhouse..using the manure as a
compost pit as
Bill Mollison did in his Introduction to Permaculture..and you can even bury things under things..like putting a cold storage system into the side of a hill with soil on top..or even sod roofs to grow things on top of a building.
another interesting thing I don't hear about a lot is using birds to bring in seeds by putting perches such as posts or fences around the property..i do that a lot here and have gobs of bird planted things, esp currants and other small berries.