Solstheim

To get to Solstheim, the player takes a boat from Vvardenfell to the dock at Fort Frostmoth, the only imperial presence on the island at that time.  From there, the player can choose to follow the main quest, which deals with the locals of the island, descendants of the original Skyrim settlers of Morrowind, as well as werewolves and their daedric god. 
 
One particularly involved side quest in Raven Rock involves the founding and expansion of a colony named Raven Rock on the west coast of the island based on an economy of ebony ore mining, much like the the town of Caldera on the main island.