Only based on the descriptie details of the setting, the "Tomb" could be interpreted not as a burial place itself but rather as a metaphor for a dark place where cruel things happen and no one would ever wish to go. Due to the somber and heavy atmosphere ("the heavy heat of the courtyard"), it could just be a place where slaves are kept and where horror and dispair ("the air was motionless", "nobody attempted to...") are the main characters.