[6: 119.1 - 120.2]
Quivi discende un rio, non lunge al ponte,
Da l'un de' cinque fonti, anzi dal primo,
Ché cinque son, pur come gradi in monte,
Per cui s'ascende al sommo insin da l'imo.
L'altro rio si rivolge al propio fonte
Lucido, puro, netto e senza limo;
Così quel corre a l'alto, e questo al fondo.
O sacra meraviglia ignota al mondo!
Ma l'uno e l'altro pur torce, e deriva
Misero error fra l'opere terrene.
Here, not far from the bridge, a river flows down from one of five springs -- the first one in fact, as there is five of them, like natural stairs in a mountain, letting you climb it from the base to the top. The other river turns back towards it own spring: shiny, pure, clean, mudless. Therefore, the former flows upward and the latter downward, O holy wonder, unknown to the world! But both keep turning, and create miserable errors among the earthly works.
These five mysterious, all too clearly symbolic rivers did not appear in Gerusalemme Liberata; they have been added in the Conquistata, both here and later on, when a more detailed description will be provided. Scholars have interpreted them as a reference to the Thomistic doctrine of knowledge, but there might be more to it, in the light of the importance attached by the poet to their cosmic meaning. Anyway, imho, this is the most unconvincing section in GC.