Well, apparently the universe is actually flat, at least according to WMAP and BOOMERanG experiments, with a high degree of confidence (0.4% margin of error).
https://en.wikipedia.org/wiki/Shape_of_the_universe
Its curvature is just high enough to support our existence, but within such narrow bounds that it can be considered flat. The donut model dates back to 1984, I'm pretty sure more modern testing methods have ruled it out, but we'll probably never know for sure - infinity is hard to measure.