Google shows some set ups if you put Duna Multy and click on images - this thread also has some nice setups of Duna Multys and Zoozone 1's (same size cage).
Zoo zone 1 please share set ups
I think I'd go for a subterranean house with a lift off top. Maybe one of these, or make one from a shoe box
Ferplast Guinea Pig House Wooden Small Pet Nesting Box: Amazon.co.uk: Pet Supplies
ie stand it on about an inch of substrate and pile the substrate up around it with a tube or tunnel leading to the entrance door. Then you can have deep substrate for digging in the rest of the cage. You'd probably need the wheel stood on a shelf if you had deep substrate. If you're feeling flush, Rodipet makes some nice platforms. This one for a 20cm wodent wheel to sit on top of
https://www.rodipet.de/shop/zubehoer...obo-wheel.html
Or this corner platform - although this would be too high to have the wheel on top
https://www.rodipet.de/shop/zubehoer...mit-rampe.html
These seem popular with dwarf hamsters too, as hidey places and toys
Rosewood Boredom Breaker Small Animal Activity Toy Sleep-n-Play Cheese: Amazon.co.uk: Pet Supplies
I can recommend one of these tunnels too - I got one for Charlie recently and he loves it - he loves the hole on the side and went in and out of it loads of times and seemed to like chewing it too.
http://www.amazon.co.uk/gp/product/B...rch_detailpage