The reason the rat sputnik is at the front there with a tube leading to it from a shelf (for easy access) is because all our hamsters have enjoyed sitting in it looking out
If you put a bit of bedding in it. It works without the tube as well because the cage is low enough they can just climb in from substrate level if you have enough substrate in.
Our first hamster Charlie used to like climbing in and out of the cage from it onto the open door (his cage was on the floor though so I use a tube instead now). He was huge by the way. Here he is in the sputnik.
The big word these days for hamsters being happy in a cage is "enrichment" which is basically variety, different textures, places to go and things to do but also things that enable natural behaviours like hoarding under their nest, having separate areas for sleeping, hoarding and peeing and things to chew. A lot of hamster toys are unsafe though so ask on here if you're thinking of getting any. Open rung ladders, toys with fabric and chains are all unsafe. Some are badly made and have nails etc. But you can use plastic cable ties or sisal string (safe to chew) for attaching things to bars.
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