Caves are unlike any other terrain on earth. Devoid of natural light, straight lines, or creature comforts, these spaces are entirely disorienting to the human mind. Caves thus serve as symbolic terrain in the imagination and provide the framework through which we will explore select Old and Middle English texts. As we go spelunking, we will uncover how medieval writers used cavernous landscapes to probe the boundaries between the visible and invisible, the human and the monstrous, the living and the dead.