The Legend of Zelda: Ocarina of Time had portals, before Portal.
In the MinnMax interview, Goddard (who was also responsible for the Spaceworld 1995 Zelda tech demo) worked on a separate tech demo to push the capabilities of the N64 console.
“When I saw Portal I thought ‘oh, actually, I had that running on the N64, I should have released it then’,” he joked.
It was basically a demo of actual portals that you could see through to other parts of the map.”