Facilis decensus Averni
Noctes atque dies patet atri ianua Ditis
Sed gradum revocare superasque evadere ad auras;
Hic opus, hoc labor, est.
The descent to Hell
The doors of Hades
' hall stand open night and day
But to retrace your steps and climb out to the skies above -
Here is the task, and this is the labour.
, Book 6