There are various "hamster houses" for sale in pet shops and a hamster will use these for nesting in.

It is important that any hamster house has a ventilated top or open front to prevent condensation building within the house which can lead to the hamster and its bedding becoming damp.

Although all hamster houses sold at pet shops are suitable for Dwarf hamsters, some with small windows or doorways may not be suitable for Syrian hamsters who can become stuck trying to squeeze through so if buying a hamster house for a Syrian hamster then ensure that all doors and windows are large enough for a full grown Syrian hamster to pass through easily.