Super Mario World: Vanilla Dome 2 (Secret Exit) & Red Switch Palace

You'll find the Key & Keyhole of this stage earlier than you are able to reach it.

The entrance to these things are blocked off by brown blocks. You'll have to go around a few of them to find a P-Switch that can turn them all into coins. Then you can make you way back to the entrance and go from there.

Finding the Secret Exit of this level unlocks the Red Switch Palace. Just get to the end of it to turn all of the red outlined blocks into Red ! Blocks. Unlike the Yellow & Green ! Blocks, the Red ! Blocks don't give you anything beyond being platform. It would've been nice if they yielded Fire Flowers...

Oh well. Only one more Switch Palace to go!