Juan Pablo Castel is the main character in the novel "The Tunnel," written by Argentine author Ernesto Sabato. He is a painter who becomes obsessed with a woman named María, leading him down a dark path of jealousy and despair. Castel's introspective nature and troubled psyche are central to the story, reflecting themes of isolation and existential angst. The novel, published in 1948, explores Castel's inner thoughts and feelings as he grapples with his emotions and the complexities of human relationships. His character serves as a representation of the struggles faced by individuals in a chaotic world, making "The Tunnel" a significant work in Argentine literature.