In the limestone islets of Halong Bay's, there are many caves, but you can't visit them all, even the ones you want. The Vietnamese government and army have everything very organized. Hang Sung Sot cave is one of the largest, with three huge chambers that can only be accessed by a small boat. The big boats are anchored in the small bay right in front, and personally, I thought that they were the best part of the visit. The entrance to the cave is at a certain point. There are a few steps to climb, and with the heat and humidity, it's a bit of a challenge. At the top, there is a wonderful aerial view over the islets and boats.