Kalev was the great primordial giant of Estonian folklore, who came from across the sea in ancient times and built the kingdoms of the Estonians; his son Kalevipoeg ("Kalev's son") was the hero of Estonia's national epic. Kalev himself died before his son was born, and was buried beneath a great mound at Toompea in modern Tallinn; the mound, the legend went, was the heap his widow Linda piled up as her grief, every stone a tear shed over her husband's death.
Kalevipoeg grew up to be a giant of legendary stature, who could lift boulders that ten men could not move, who plowed his fields with such vigor that his plow churned up the great Lake Peipus. He was the prototypical Estonian hero — strong, blunt, often violent, slow to think but quick to act, sometimes the unwitting cause of disaster. The cycle of his deeds includes the long quest for a sword (which was forged for him by a blind smith and which he later lost in a river — he never recovered it, and the lost sword became one of the legendary objects of Estonian folklore), the war against the Sons of the Witch (an ancient tribe of antagonist beings), and the great voyage to the world's end where he attempted to reach the doors of heaven and was turned back.
His death came in a strange episode. Kalevipoeg, ferrying home alone after a long expedition, fell asleep with his feet in the river; the lost sword (which had fallen into that very river years before, and which had been told by Kalevipoeg himself "to cut whoever should walk upon it") cut off his legs at the knee. He bled to death there at the river's edge. After his death, he was made the gatekeeper of hell — set to chain the great enemy-hound at the world's end, just as the Slavic Zoryas are charged with the chain of the doomsday-dog. So the dead hero became a guardian of the underworld, and his strength preserved the world from final ruin.
The Kalevipoeg epic was compiled by Friedrich Reinhold Kreutzwald in 1857-1861, in conscious imitation of Lönnrot's Kalevala; the result was the foundation document of modern Estonian literature and a key text in the Estonian national-cultural revival of the nineteenth century. Where the Kalevala is largely oral material with editorial framing, the Kalevipoeg is more substantially Kreutzwald's own composition built around traditional material — a literary epic in the romantic mode rather than a strict folk compilation.