The Pacific Islanders navigated the great expanse of water by looking at the stars by night. Little did they know that the stars they looked at held so much more surprises for them. One fateful moment, their chief disappeared for several days and when he returned, he was a changed man.
Upon his return, he told of stories of advanced beings from another dimension who shared their technology while everyone thought he had gone away. Time dilation was a reality in the passage between the two worlds.
From then, these islanders hid their technology in the subterranean tunnels carved out by the volcanic activity of their homes. This is a scene from one of their subterranean labyrinths.
Henceforth, they became the masters of the sea, reaching vast lands toward every point and established great cities everywhere.
Soon enough, their skill of navigation and the technology they possessed paid off and they established great cities on the larger continents as they journeyed all over the Pacific and beyond.
Armed with the technology and the knowhow for navigation, the Islanders sailed beyond the atmosphere and helped establish Earth's first colonies beyond the stars.
This alternate reality comes from the what if of the great explorations in the 16th and 17th century. Instead of Magellan and Columbus sailing around to discover new territories, the native Pacific Islanders did that with the help of a benevolent race from another place.