Only down onto it, from a place with a way down to where it is: then the jumper is in the barrel, with it, and a player is shown the place. From anywhere else it is "you cannot jump onto the ... from here." -- or would be: where the way to it is not down, the code has JP NZ,MSG_CANNOT_JUMP_ONTO_FROM, which jumps into that message's bytes rather than printing them, apparently for LD HL,MSG_CANNOT_JUMP_ONTO_FROM and JP RUN_MESSAGE_HL. In a quick test, from the great halls beside the cellar, that path was not reached; whether anything can reach it is not worked out.