From the start, go around the outside of the cage to the right. From about half-way around, balance on the edge of the cage. Nearly the full way around (over lava, of course) the entrance to a secret room with goodies.

Find the red door. Close to it, in a small cave, you will find a switch that lowers the platform leading to the red door. Activate the switch, ride the platform up. Jump down again (across the lava) and go back to the switch. A tunnel leading to goodies and trouble opens on either side of the switch.

Get on the crown at the back of the castle. About halfway around, if you stand on the corner, there is a shootable switch. You will hear a door open behind you. To get to it, first jump forward - into the lava - to get the asbestos suit.

Get the yellow key. In the back wall, there is a cave entrance. Secret room with goodies. You just have to... cross the lava!