 The pass, which was built in 1585 in the Ming dynasty, has been repaired and expanded over the centuries.The existing wall, built in 1982, is 24 meters long, 7 meters wide and 5 meters high.To the northeast of Nan'ao Island, there is a small island not far from the coast, with a total area of less than 1,000 square meters, known as "Treasure Island."