Inferno, Purgatorio, Paradiso
Dante Alighieri's epic poem (1308-1320) journeys through Hell, Purgatory, and Paradise, creating a complete cosmological and moral universe in verse. Written in vernacular Italian rather than Latin, it elevated everyday language to the highest literary art. Its terza rima structure (ABA BCB CDC) creates an interlocking chain of meaning.
Invented the concept of 'world-building' in literature. Established Italian as a literary language and proved that the vernacular could achieve the grandeur of classical languages.