Merlin's cage:
The main cage is a Fantasia three storey. Luckily its tubes connect onto Crittertail rings that connect onto Habitrail tubes and units. I also got him a Habitrail Orbitting Satellite as they are 9.5 inches (he's hardly set a paw out of it all evening!) and a Habitrail spaceship. I managed to connect his Dora the Explorer bit with a kitchen knife and some careful engineering.

Whole setup:


Main cage:


Dora the Explorer! and orbitting satellite:


Spaceship:


Merlin himself: