It is in the 小門地質公園 at 西嶼. It is not really cave but a natural bridge caused by erosion. It is interesting to see, but it is better to hike to the end and see the 跨海大橋，it gives the best view of the bridge.
You can spend an afternoon browsing the exhibits at Xiaomen Geological Museum during your trip to Siaomen Island. While you're in the area, stroll along the marina.
After visiting Zhuwan Dayi Temple, make a plan to see the other sights and activities in Xiyu. While you're in the area, wander around the natural setting.
You can spend an afternoon studying the exhibits at Xiyu Crab Museum during your travels in Xiyu. While you're in the area, stroll along the marina.
Explore the waterfront in Xiyu with a trip to Heng-chiao Fishing Harbor. While you're in the area, wander around the natural setting.
You can find out about the history of Tongliang when you stop by Penghu Great Bridge. Amble around the area's marina or visit its monuments.
You can learn about the history of Tongliang with a visit to Tongliang Great Banyan. Wander the seaside and beaches while you're in the area.
