The Penghu archipelago is primarily composed of basalt, formed from repeated lava eruptions through cracks in the Earth's surface, cooling and solidifying over time. The earliest volcanic lava dates back around 18 million years, with a calm eruption that ceased volcanic activity approximately 8 million years ago. Penghu's basalt formations have created a square mountain landscape, with steep rock walls. Over time, these formations have been shaped by weathering, wind erosion and coastal erosion, developing various unique topographical features. Additionally, the lava's rapid cooling causes tension in the rock, resulting in the formation of polygonal columns, known as columnar joints. These joints can be found in straight, curved or inclined patterns, making them a distinctive feature of the Penghu basalt landscape.
In Magong, along County Highway 201 heading towards Fenggui, you can find the towering columnar basalt formations of Qingwan on the left side of the mountain. The basalt in Penghu has been weathered and eroded over time, revealing a variety of forms, and Qingwan is one of the most scenic examples of columnar basalt in the region. At Qingwan, visitors can not only admire the magnificent, solitary basalt columns but also enjoy the surrounding coastal scenery. 
Recommended Duration of Visit: 1 hour

Source: Penghu Travel