On July 24, 2020, a vast amount of source code from Nintendo's early consoles surfaced as well as prototypes and assets from games such as Yoshi's Island, Super Mario Kart, The Legend of Zelda: A Link to the Past, and more.
The leak included a portion of Super Mario World's source files with an absurd amount of early assets. While some had previously been found in the SNES Test Program and SNES Burn-In Test Cart or had been glimpsed in grainy magazine screenshots, many had been completely unknown and show how significantly the game changed over its development cycle.
Within leaked Super Mario World development files multiple iterations of the overworld map were found.
This version is dated 26 October 1989 09:49 and shows a much different design to the final version, including a stylized mushroom island.