Another vote for rat tubes and sputniks hanging from the cage roof
My Syrians love going up their tubes and sitting in their sputniks to stare at me! And I find the sputniks are great for dropping treats in too. I use the hamster sized ones but without the tops, rather than the rat sized ones -- the hamster ones are a bit of a tight squeeze for a large Syrian with the tops on, but without they're fine, plus then I can use the tops as Robo houses
