Nor could thy fabric, Paul's, defend thee long,
Though thou wert sacred to thy Maker's praise:
Though made immortal by a poet's song;
And poets' songs the Theban walls could raise.
The daring flames peep'd in, and saw from far
The awful beauties of the sacred quire:
But since it was profaned by civil war,
Heaven thought it fit to have it purged by fire.
[Excerpt]
These are verses 275 and 276 of the 304-verse poem. The original St Paul's Cathedral burnt down in the Great Fire of 1666. The current cathedral was built over the ruins of the old and completed in 1711.
Other excerpts from this poem by Dryden are also on Poetry Atlas.
As are many other poems about London.