It's a mod adding a new world called Dixieland.
New locations, new interiors, new npc, new enemies. 
The entrance is in the boat stranded near Atom Cats Garage. 
If you want to leave Dixieland (Fast-travel is impossible), use the console command
coc SanctuaryBasementJahani, you are teleported into the Root Cellar Sanctuary.

Installation:
- Exctract Esp file to your data folder and enable it.

Requirements:
- Far Harbor

Future plans:
-Expansion of the territory
-New settlements
-Quest lines
Work continues...

Credits: 
argill for the idea, help and support.
aliceschall for the English translation.

Sprint doesn't work in the new world. In order to avoid Sprint Bug you must add the following line to your Fallout4Custom.ini:
[Gameplay]
fPlayerDisableSprintingLoadingCellDistance=0

Unfortunately, I can not translate into English a new version of the mod. If anyone wishes to do this, I will be very happy.

Credits: Elianora for the glasses. Many thanks!