What environmental themes would you like to see as an island/open zone area in future Sonic games

[Shiny Gems]

Now, as we all know, Sonic Frontiers had the open zone gameplay in it, which was basically like the open world from The Legend of Zelda: Breath of the Wild and The Legend of Zelda: Tears of the Kingdom. In it were three environmental themes, not counting the last two islands.

There was a grassy island.

There was a desert island.

Finally, there was a volcanic island.

And since Sonic Team is likely to use the open world gameplay again, there will probably be room for more environmental themes to add. That said, what environmental themes would you like to see as islands or open zone areas in future Sonic games?

I'll start off. I would like to see islands or open zone areas with an ice theme, a city theme, a casino city theme, a jungle theme, maybe even an ocean theme, or a ruins theme with lots of ruins, more than what were on the islands in Sonic Frontiers.

So, what about you all? What themes would you like to see for islands or open zone areas in Sonic games?