When you open the door in front of you, you may catch a glimpse of an SS disappearing to the right somewhere ahead.
Finish the first few SS before moving on. You will notice the treasure behind the columns. This works as a hint about a short cut later in the level.
You need the Gold Key to get into the green maze. There are two ways to get it. One is to take on all the enemies in the grey stone area. Another is to challenge a Grosse brother in the north-eastern part of the purple area. A chaingun is found there too.
When you get into the maze you have two possibilities. The long way or the short cut. Once you are in the south-western part notice that many secret doors eliminate the use of other both ordinary and secret doors. But whatever you do it is still possible to get to all the rooms.
There are two Silver Keys as well. One is found deep inside the maze, the other in a room with another Grosse brother.
The elevator can be entered from opposite directions.
This level offers a lot of treasure and several 1-ups.