Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4877248.
I designed this playground piece for my daughter's hamster, Brad. Brad was bored (I don't know how she could tell, but that's what my daughter told me), so I designed the ladders and tubes to be a little challenging. The top is an observation deck, but it isn't high enough to be a fall hazard. Brad is happy now.
All pieces are printable in PLA without supports. Obviously, PLA can have colorants and additives that are not good to consume, but that's the case for pretty much all plastic rodent toys sold in pet shops.
The tubes and their connections to the deck must be bonded together. Although the ladders lock together and to the deck pretty well, you might want to bond them together, anyway. In case your hamster likes to chew its plastic exercise equipment (Brad doesn't), make sure you use a benign glue or solvent. I won't get into how different glues stack up in terms of potential harm to rodents, but my solution was to weld the pieces together using dichloromethane. Dichloromethane is nasty stuff, so if you decide to use it, wear a chemical respirator, nitrile gloves, and do the work outside. The good thing about using dichloromethane is that it is a volatile solvent, and fully evaporates quickly, leaving no residue (I gave it a couple days, just in case). BTW: dichloromethane is sometimes used to remove caffeine from coffee beans to make decaf.