After creating a raft or a boat, multiple islands become accesible.

The Complete Map. Note that City island apears in different places, not just this one, the comment said.
Boar Island[]
Boar Island, located just west of the main island, closest to the main island.

Sailing to Boar Island with a Boat
Items:[]
Enemies:[]
A Group of Unuseful Islands[]
An island with nothing.
Rain Flower Island[]
The only island with rain flowers.

Give the rocks a hug to enter the island.
Items:[]
Lion Island[]
Lions' habitat.

Lion Island
Items:[]
City Island[]
The goal of the game.

City ISLAND!!!
Buildings:[]
Mysterious Tree Island[]
A mysterious tree. 15 times harder to chop than Teak Tree.

Mysterious tree location

Mysterious tree