Built upon the island are two of the three runic stones of the planet: the Marked Stone and the Eclipse Stone, which lie upon the northern and southern penninsulas respectively. The only city on the island is Proxim-City, where all the local residents live. This city is also the home to the Maritime Museum, dedicated to the pirate LeBorgne.
Twinsen comes and goes from Proxima Island many times throughout his first adventure. Among the things he accomplishes on the island are stealing LeBorgne's treasure from the museum, getting a Proto-Pack from Jerome Baldino and releasing the two runic stones.