|Who really knows
The Deep is a natural phenomenon in Greater Pixlton, first discovered in 1986. The main part of this phenomenon consists of a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater, similar to a cenote. It was formed by the dissolution of rock and the resulting subsurface void, which may or may not be linked to an active cave system, and the subsequent structural collapse. Rocks that falls into the water below gets slowly dissolved, creating space for more collapsing. It is likely that the rate of collapse increases during periods when the water table is below the ceiling of the void, since the rock ceiling is no longer buoyantly supported by the water in the void. Due to rising sea levels, the structure is now fully submerged and considered the deepest part of the island and its surroundings.
Researching the feature is proving rather challenging, given that the depth of The Deep is unknown at this point. No expeditions have made it to the bottom, not even those using unmanned vehicles. What makes it especially hard is the different currents that sweep through the underground caverns, taking divers into places they probably will never escape. Therefore, what lies below is entirely unknown. Surely, it's not a portal to a different dimension. The only thing ever recovered from the deep was a human bone wearing a crudely made golden bracelet with a chicken pendant.
The area directly around The Deep consists of a few islands, some of which are more interesting than others. A particularly uninteresting area is that of the The Uninteresting Isles. We could write some elaborate story on these two islands, their history and all the incredible stuff that happened here over the ages. The truth is that absolutely nothing of interest happened here. Like... ever... They're two separate islands, but depending on the tide they merge into one. I guess that's a noteworthy little factoid.
Another island directly bordering The Deep is Idris Island. Famous for being the only island in the area to house flamingos. They adore the vegetation that grows here. It is said that it acts as a hallucinogenic for the pink birdies. The island is named after the actor that all Pixltonians revere the most. He is a bit of a big deal here. Every time he visits, a parade is held in his honor. So far he hasn't visited yet.