Spiral Mountain serves as Banjo & Kazooie's home stage. I never got into the N64 classics, but apparently all the games start you there. Think of it like Green Hill Zone in the Sonic series, but for Banjo and his bird friend.
The stage isn't too wacky.
But from what I could look up, it's pretty faithful to the games. Gruntilda (Banjo's nemesis) has her face in the mountain, just like the games.
The stage doesn't move around but it slightly turns and it does make things somewhat interesting without going overboard.
Probably my favorite of all the DLC stages so far.