North Anvil Islet

Penghu has two Anvil Islets, named for their resemblance to an anvil. One of them, North Anvil Islet, which belongs to Baisha Township, is an uninhabited island located offshore northwest of Penghu Main Island. Its main body is composed of a basalt mesa plateau, surrounded by steep sea cliffs. The volcanic breccia underlying the columnar basalt is relatively fragile. Due to the influence of the northeast monsoon, the rock layers on the north shore have been long-term scoured and eroded by ocean currents, forming a massive sea cave. Even small boats can enter this cave, which is larger in scale than the Blue Cave of Xiji Islet, making it Penghu's largest sea cave. Inside, as no sunlight reaches, the temperature is three to five degrees lower than outside, earning it the nickname "Air-Conditioned Cave."