disclosed is a collapsible , portable container having a roof , a base , two foldable end walls and two removable side walls . the end walls and side walls of the container are load bearing elements having a twinned wall structure made of rotomolded plastic . the container is collapsed by removing the side walls and inwardly folding the end walls to draw the roof closer to the base . the load bearing capacity of the end walls and the side walls can be increased by arched indentations formed within the twinned wall structure .