zhè / zuò / gǔ / chéng / yī / shān / ér / jiàn / fáng / shǒu / yán / mì / gù / ruò / jīn / tāng

这座古城依山而建，防守严密，固若金汤。

This ancient city was built against the mountains and is defended so strongly that it is virtually impregnable.