Tip: Switch palace switches normally disappear if you replay the level. However, if you insert them as direct Map16 and use the hex-edit at $00EEB2 in the ROM map, you can replay the level without a problem.
Contains two blocks that act as a midway point. One acts like a somewhat regular one, generating a sound and setting the midway flag. This one can only be activated from below (though you could move the labels around to change that). The other one should be used as an invisible midway point blocks - it doesn't give off any indication that you reached the midway point, but it does set the flag.