One of the most popular sites for tourists around Halong Bay is probably Song Sot cave. It is included in the itinerary of nearly every single Halong Bay cruises.
This cave, one of the largest in Halong Bay, is located on a larger island near Cong Do area, where most cruises stay overnight, so this is one of the reason why it is covered by nearly every cruise.
You get to the cave via a wooden pier, and you have to walk quite a few stairs to the entrance of the cave. If you have walking difficulties it will be a challenge to get to the middle of the island where the cave is located. On the way up you will have a few great views over the bay – so it is worth it to turn away from the stairs and the island.