JoJoLand is a pair of islands, somewhere over the rainbow. The main island is in the shape of a banana where the stalk (where you usually peel from) faces to the west and the base (the short end) face to the east. A small island to the east of the main island is Micro City.
The main island is broken down into four areas: JoJotown, Alpacatown, Bearland, and Willyville. The westernmost land is Willyville, near the "stalk" of the banana. It extends about a quarter way down the banana, where JoJotown begins. This town extends down to just over half of the banana. Here, Alpacatown, the smallest town on the main island, begins. It's width is approximately that of the island of Micro City, which is just north of Alpacatown. Finally, the rightmost third of the main island is Bearland. This extends to the base of the banana.
The stalk and base of the banana are fields of banana farms, where the island gets their source of bananas. At the border of the stalk and base of the banana, there are invisible borders infinitely high, which JoJoLanders cannot walk through. However, the current ruler of the land, Kolo, has the ability to walk through these borders without being affected by them. This is how the bananas go from the farms to the island.