“When he got to Bilbao a month before [the Guggenheim Bilbao] opened, says Frank Gehry, ‘I went over the hill and saw it shining there. I thought: ‘What the f*** have I done to these people?” … The museum was opened 20 years ago this month, by the king and queen of Spain, since when it has become the most influential building of modern times. It has given its name to the ‘Bilbao effect’ – a phenomenon whereby cultural investment plus showy architecture is supposed to equal economic uplift for cities down on their luck.” Rowan Moore looks at Gehry’s icon and his thoughts about it (he hates the idea of a “Bilbao Effect”) and at why the phenomenon hasn’t worked so well in other cities that have tried it.