Not to be missed, of course, is the running wheel. I use the 21 cm wooden running wheel from Trixie, but this time I also use a 20 cm Wooden Running Disc from Trixie as an extra. A running disc is great for a hamster if they are the right size.
What is very important is that a running disc cannot replace a running wheel. So there should always be a normal running wheel in the hamster enclosure.