消滅 しょうめつ可能 かのう せい都市 としだったら
shōmetsukano useito shidattara

Noun
Da Copula

The "-tara" conditional form ("if/when…") of 消滅可能性都市

1. If it were a city likely to be destroyed; If it were a city facing possible annihilation

Tara Conditional