Pengjia islet is also named Dazhishan Islet or Cao Islet and the local fishermen often call it the big islet as it is the biggest one among the three outside islets of Keelung. Similar to Mianhua Islet and Huaping Islet, this plainer islet was also formed by volcano eruption. In the past, some fishermen stayed on the islet, but one can only see the lighthouse and meteorological observatory now.
　　 Standing alone in the outer sea, Pengjia Islet has no natural barrier to withstand monsoon and typhoone; hence, the only plants that can survive on the islet are bushes. Accordingly, albatross used to breed here, but currently, one will only see some seabirds taking a break near the marine cave.
　　 This islet remains a military control district; hence, citizen is not allowed to visit the islet. However, one might be able to see the islet by taking a fishing boat to sail around the islet.