Mapmaking 101 - Secret Passages and Caves, Part 2
Secret Passages and Caves
Part 2By Kolja Silvani
Adapted to English by Jayhawk*
The original article can be found here
An interesting part of making secret passages is the art of
creating an entrance
The simplest way to hide the secret passage is to just let it be
part of the surrounding landscape. This will make the entrance
virtually invisible.
Picture 4: A hidden entrance.
A second option is to use a staircase to provide access. You'll need to start with a straight section of secret passage, its height depending on the height of the plateau. To reach a maximum height plateau you need 11 spaces in a row. Do not try to build this along the diagonal, the staircase must connect side by side in a straight line! At one end of the passage you raise a piece of land that's high enough to allow a wall placed here to just break the surface of the plateau. Next you lead a staircase down into the depths of your passage.
Note: It seems perfectly possible to use a more curved kind of
staircase, like one making a zig-zag. However, there needs to be
straight sides connecting, not corners.
— Jayhawk 
Picture 5: Staircase leading down.
A variation on this idea is not to place a staircase leading downwards but a ladderman. This guy can be moved around during the game of course. Keep in mind though that not all troops can use ladders to climb up. In order to get this to work correctly, you'll need to use a bit of enemy wall as the access point; otherwise the ladderman won't connect and the passage will be inaccessible. The picture shows a leveled view, making the ladderman and the climbing soldier clearly visible. The wall of course looks better in normal view.
In any given secret passage or cave (these will be discussed more
fully in part 3) you can use a lot of these barriers. For
instance you can set an enemy wall at the lowest level to keep
the soldiers within the cave system. When you have ladders on
both sides of the wall segment you get to see your troops climb
up one ladder and down the next, adding a lot of drama to your
cave. A group of soldiers snaking its way through a series of
passages this way looks absolutely great.
Of course, there's a lot of other things you can do using this
basic idea.
Picture 6: A ladderman entrance.
Another interesting option is to use a gatehouse as the entrance
of a secret passage. When the gatehouse is in your own colour, it
effectively locks the enemy into the caves. An important thing to
remember is, that if you want to use a gatehouse this way, a
small section of the terrain needs to be below the level of the
gatehouse's deck, as can be seen in the blue box on the image.
The best way to check this is so is when the stones of the wall
of the gatehouse are visible.
Picture 7: A gatehouse as entrance.
Using passages you can connect two seperate castles or a castle and a village. Or you can have a passage lead off to an iron deposit.
Another interesting option is to build a passage into an enemy castle, with a section of enemy wall at the end (as explained in a previous paragraph). This will make it seem as if your army has dug its own tunnel into the castle. As you can see there's lots of ways to use these passages.
In the third and final part of this workshop we will look at making caves.