‘…those who have rightly understood me will be bound to realize that even architecture might acquire a new significance thanks to the spirit of music on the basis of which I planned my work of art and the place of its performance and that the myth of a city built by Amphion’s lyre has not yet lost its meaning.’
While Wagner is talking here about his new theatre at Bayreuth (he is laying the foundation stone in 1872) he suggests that this building provokes and offers an example of the development of a German style of architecture that sets aside conventions and ‘traditional arrangements’ (implicitly French) in order to meet an ‘ideal need’. So the arts, because they exemplify the ‘genuine inner need’ of a people, generate re-building – of a theatre, of a city, of a nation. Though the phrase about a city built by Amphion’s Lyre could, I think, mean many things.
You can find the speech quoted at length (in English) at: http://www.bayreuther-festspiele.de/documents/_the_bayreuth_festival_theatre_341.html