Hiroshima.

Sorry, had to make the dark joke.

The serious answer is the first Apollo launch. Because space. That’s when real space ventures became a reality rather than a dream.

Tbh though, if it was some kind of magical thing where it was possible, the moon landing would be a bigger deal for me. But there’s no way without going into fantasy for that to happen, and it wouldn’t be the same because part of the cool part of this idea is being there, in person, with the ability to experience the entirety of the event. Can’t cram another person into the lander at all, and that’s where I would want to be. But I’d be perfectly happy to be in the crowd watching a launch