What is the specific punishment for the heretics in the sixth circle of Hell?

In Dante's Inferno, the punishment for heretics in the sixth circle of Hell is that they are entombed in fiery graves. This reflects the heretics' denial of the immortality of the soul and their rejection of religious truths during their lives. The burning tombs serve as a fitting retribution, embodying both the physical agony of the flames and the metaphorical implication of being spiritually dead—trapped in a state of eternal suffering, much like how they rejected the eternal truths of divine doctrine. This punishment symbolizes the consequences of their choices and beliefs, emphasizing the theme of divine justice that runs throughout the work.