Small animals such as mice, hamsters and gerbils need housing as a hideout in their cages. They need retreat opportunities for resting, nesting and playing. Many of the available houses for small animals allow to climb on them and explore them from all sides.
An important thought before choosing a model is that will it fit your pet’s cage, is it too big or too small for your personal situation. The retreat house shouldn’t take all space in your pet’s cage. Your pet needs still some place for playgrounds, chew toys and more.