Cool idea. I would visit the Minecraft universe, Dc Universe, marvel universe, and Star Wars universe

Marvel Universe/MCU, Dc Universe, My Hero Academy Universe, SCP Universe, H.P. Lovecraft Universe (Multiverse), Gyee Universe, Tokyo Afterschool Summoners Universe, Fairy Tail Universe, Forgotten Realms/DnD Universe and Hunter x Hunter Universe

Mainstream marvel universe/MCU, mainstream DC universe/Arrowverse, Dragon ball z universe, Harry Potter universe, Assassin's creed universe.

These are my top 8 universes I'd want to visit if I could.

- DC Animated Harley Quinn universe

- Edens Zero universe

- Faiy Tail universe

- Marvel Cinematic Universe

- Naruto universe

- Twin Star Exorcist universe

- Wakfu universe

Honestly my first choice would be the Pokémon universe, followed by those of Naruto, fairy tail, and yugioh, after that I'd explore the universe of Bleach and the Highschool DXD universe. Lastly would be the universe of Rick Riordans books. But I'd probably spend most of my time in the Pokémon universe as that's the supposedly fictional universe I've devoted the most time and energy to contemplating. Besides even though I'd miss the universe I now inhabit the lure of adventure and in-depth study has always been nearly irresistible to me and what's better research than to experience it first hand.