守着一座空城等着一个旧人
[shŏu zhe yī zuò kōng chéng dĕng zhe yī gè jiù rén]
'Guarding an empty city waiting for an old friend'. This portrays longing and nostalgia for past relationships or people who used to mean a lot in one's life. Waiting for that person implies unresolved feelings, unmet expectations, regret or the yearning to return to the good times they once had.