In this excerpt from annus mirabilis john dryden speaks about london after it was ravaged by the great fire

The stanza that illustrates that the city of London is looking ahead with renewed vigor is this one: "Me-thinks already, from this chemic flame, I see a city of more precious mould: Rich as the town which gives the Indies name, With Silver paved, and all divine with Gold." In spite of the calamitous nature and devastating effect of the Great Fire (1666), which Dryden describes so vividly in this famous and extensive historical poem, the author chooses to be optimistic and hopeful, and he even ventures to compare post-fire London with the prosperous city of Mexico ("the town which gives the Indies name"), then under Spanish rule.

the underlined phrase is an example of : understatment