A rigid suitcase includes first and second shells defining a first storage volume, the outer surface of the first shell including a recess, and an auxiliary container defining a second storage volume, physically separate from the first storage volume, and adapted to be moved between an inserted state in which the auxiliary container is at last partially housed in the recess and a removed state, in which the auxiliary container is completely extracted from the recess. The rigid suitcase further includes guide members operable to guide the auxiliary container as it moves from the inserted state to the removed state and vice versa, and removable attachment members operable between the first shell and the auxiliary container and adapted to be actuated between an attached state, in which the auxiliary container cannot be removed from the recess and a released condition in which the auxiliary container can be removed.