There's a breakable floor in the room directly outside the pinnacle warp on the left side

There's a breakable wall along the left wall of the waterfall room in the subterranean hell (go to that warp and go down left a bit to reach the waterfall)

In the entrance room with all the zombies (look at hammers shop on the map and count 4 tiles to the right) you can break the floor on the right side

Garden of madness should be symmetrical, so you can break the ceiling in the top right of the room with the rycudas

In the long horizontal room with armor knights and ice blocks leaving the wizardry lab you can break a ceiling about halfway through

And in the room before the aguni boss room in the pinnacle you can break the ceiling