空城空梦空欢喜旧人旧事旧时光
[kōng chéng kōng mèng kōng huān xĭ jiù rén jiù shì jiù shí guāng]
Each '空' means empty; so it’s about 'empty city, empty dreams, empty joy'. The second part ‘旧’ means old, referring to 'old people, old things, old times'. Together, it suggests feelings of emptiness and nostalgia for lost relationships, experiences, and bygone days. A very melancholic tone.