Well is it? Im having a hard time trying to find good lvling spots, any help?

Ive done so far:

Twilight Town- Roxas][ DONE
Twilight Town- Sora, Donald, Goofy ][ DONE
Hollow bastion- Sora, Donald, Goofy ][ DONE
Land of Dragons- Sora, Donald, Goofy, Ping/Mulan ][ DONE

Lvl 16 now

Beast's Castle- Sora, Donald, Goofy

On Beasts castle, ive talked with belle about Beast's servants and stuff, And i need to go to dungeons via underloft.

I hear there's a boss, is there? And is lvl 16 good?