Volcanoe island (Forgot its name)

[Allure]

Fort Dundee is the fort on Padres del Fuego (Aka: volcano island). If you go by Gunner's shack, head towards the fort and you'll see a cave entrance on the left

[Cannon Mad Dan]

I've only seen the one on Port Royal. Was very cool when I first saw it.

[Elizabeth_McBonnet]

I seriously need to explore port royal, i have hardly seen anything there.
I didnt know that it was common i guess.