An operating variable-volume and extensible-wall construction to be transported and used as a field hospital, transmission center, observation post, control room and the like, characterized in that said construction comprises a central body, having a size corresponding to that of a standard container, and two withdrawable side bodies, adapted to define a withdrawn position, where said lateral bodies are substantially included in the central body, and an extended or projecting position where said side bodies are withdrawn from said central body, thereby defining a single extended body, said construction further comprises swinging and telescopic raising means, for raising the construction from the ground.