洞房 refers to the bridal chamber — the bedroom for a newlywed couple on their wedding night. It carries strong cultural and romantic connotations in Chinese tradition, often appearing in poetry, idioms, and wedding blessings. The phrase 洞房花烛夜 ('bridal chamber with decorated candles night') is a classic expression for the happiest moment in a person's life, paired with 金榜题名时 ('when one's name appears on the golden list of successful candidates'). You can use 洞房 in both literal (the room itself) and figurative (the wedding night) senses.