It wouldn't be a proper pirate LEGO without secret passages and long-lost treasure. Kinggregus' giant, pirate-themed build has it all, well-hidden in a massive fort.
The front side looks peaceful, as the builder described in this Eurobricks Forum post:
I figured that it would be fun to do cliffs in another colour than grey. I got inspired by the coast in Algarve to make the cliff in dark orange. I also decided to be very creative in naming my fort, and decided for naming it Fort Portugal.
As I wanted to enjoy the build as much as possible, the fort is built on both sides. I have also added some play features. This fort took approximately 4 months to build. It is build on two XL baseplate and this is by far my largest build
But the other side of the set has a lot more going on. A barrel for example in the kitchen that leads to not only a secret passage, but to a cave where sirens are protecting some forgotten treasure.
There's also an underground prison full of pirates and captains in their private cells.
Here's an overview of the back side: