Gupoyu, located to the northwest of Baisha and southwest of Jibeiyu, is an island composed of basalt, featuring a square plateau. The island spans about 1 kilometer both north and south, making it the largest uninhabited island in the Penghu archipelago. The island consists of four land masses and three narrow land strips, forming a plateau with a series of sea erosion platforms along the northern coast. The east coast(north and south sides) has two natural white sandy beaches. The basalt found on the island is highly porous, with quartz sandstone layers rich in iron on the surface, creating a strong contrast.
  
Gupoyu Harbor
On the island is a memorial stone, the "Bokhara Shipwreck Memorial(英輪沈船紀念碑)," located at the highest point. The northern sea platform has been eroded by the sea for years and is a renowned natural source of high-quality edible seaweed. Every winter, residents of Chikan Village gather in boats to harvest the seaweed in a lively, market-like scene. Gupoyu is a renowned wild seaweed harvesting site in Penghu, where the seaweed is referred to as 'black gold' by the locals. The northern side of Gupoyu is a natural, pollution-free zone for wild seaweed. The seaweed grows from late October to late March, with the winter northeast monsoons and strong waves promoting its growth. As a result, winter is the harvesting season, also known as the 'black gold' picking season. The waters between Gupoyu and Baisha are the largest fishing grounds for clove fish in Penghu, with the fishing season running from April to September. However, in May, when the female clove fish are spawning, a fishing ban is enforced to protect the species and ensure the sustainability of their population.

Source: Penghu Travel