Abstract: Various configurations of play yards and play yard mattresses are presented herein. Each of the play yards and play yard mattresses is light weight and breathable, yet has sufficient structural integrity to support an enclosed child or infant. In some embodiments, the play yards and mattresses may be collapsible. In other embodiments, play yards feature a mattress placed above a base assembly, such that an interior space is formed between the mattress and base assembly, said interior space being substantially void of any articles or other materials. In another embodiment, play yards feature a base assembly having a centrally located hub assembly comprising a release button and sliding pins.