Gupoyu is situated northwest of Baisha and southwest of Jibeiyu. It is a mesa plateau composed by basalt; extending 1km from north to south, it is the largest unmanned island among Penghu islands. The island has a lot of vesicular basalt, but the surface is covered with ferrugieous quartz sandstone, creating a strong comparison; this is truly a unique scene among all islands in Penghu.
The island houses a British Shipwreck Monument, on its east side is the silver anchovy fish ground, and the southeast side houses beautiful corals, great for surfing when the tide ebbs; the north side is the famous laver ground, Penghu island has a lot of reefs and is extremely windy with big waves during the winter, and this place is known far and wide for its abundant harvest of laver; towards the end of every lunar year, there will be a large harvest event, when firecrackers will be lit, and everybody will bring out their best skills to harvest laver, which is a blessing for them in the cold harsh winter!
The origin of the name Gupoyu has aroused the curiosity and wild guesses from many. It is said that a long, long time ago, there lived a young lady in a village, who had a boy friend whom she had loved for years; however, her parents were against this relationship and forced her to marry someone else. This frail girl decided to run away from home to fight against her parents’ decision to marry her to someone else, and also to prove that her love with her boy friend is strong. She came to an unmanned island and lived out her days with the sky, the earth, the sea and the mountain as her witnesses, days shall pass, until she is again just dust. When her younger family members visited her, they called her "Gupo" (great-aunt in Chinese) out of respect. Therefore, when the story of this girl who lived her life guarding her love spread, the story of the “Gupo” became the beautiful legend of this unmanned island!