Abstract: A portable playpen/mattress for babies is described. The playpen includes a flexible base and a plurality of substantially open walls all consecutively attached to each other. The walls are attachable to the base substantially perpendicular to the base. When the walls are attached to the base, the playpen is in an erected configuration, and when the walls are detached and folded one on top of another, the playpen is a collapsed configuration. The base is attachable to the walls in two configurations. When the corners of the base are curled around the leg portions of the walls, the base is in a rimmed configuration, and when the leg portions are directly attached to an upper surface of the base, the base is in a flat configuration. A reversible roof is selectively attachable to the walls. An outer cover is adapted to enclose the base and the walls in the erected configuration.