ByDurinsBeard:
Regarding pits: well, a channel I can dig. But how about a fifty-foot deep pit? The only way I can figure is this:
1) at z-1, dig a channel of appropriate size.
2) dig an access stairwell downward one level.
3) dig out a passage on z-2 equal in size to the channel above it.
4) dig a new channel in the passage on z-2, same size.
5) dig an access stairwell downward one level.
6) go to 3).
7) continue till you've come to the bottom.
8 ) wall off the access stairwells.
Would that work, do you think?
I use ramps (since you can clear them out behind you as your drop) and trap two good (high master or so) miners in there immediately after they have drunk. I can normally delve 6 or so z-levels (5x10) before they start complaining about being thirsty, and then I have them dig their way back to the rest of the fortress. I suggest dropping your main stairway down as far as you want your pit to go before you start the delve, so that they don't have to carve stairs upwards when they are done.
I normally put my barracks on that level so that when things fall down my military can swarm them while they are lying on the ground with broken legs (and spines, and arms, and...).
Or just fill the entire bottom of the pit with spikes and have your favorite dwarf laugh manically as he pulls the level over and over again.
The top of my entrance tends to look like
INSIDE
##XXX##
.=====#
#=====#
#=====#
#=====#
#=====#
#=====#
#=====#
#=====#
#=====#
#=====#
##...##
OUTSIDE
Key:
. = Floor
# = Wall
X = floodgate
= = Bridge
with floodgates to close off the main entrance and divert invaders through the passage on the upper left, which can lead to a maze of twisty little passages and painful death. The wider area and single tile corridor make them all rush onto the drawbridge and bunch up around the entrance to the maze, which makes it easier to catch lots of them per drawbridge cycle. Of course, if they've got trolls or other building destroyers, you'll want to trigger the bridge early to prevent them from breaking through the floodgates, but a few military dwarves should be able to take down unconscious trolls with broken legs pretty easily. Or, again, the spikes.
I suggest building another retractable bridge at z-1, so that you can close off the pit and prevent archers standing at the entrance from firing down at your military in the pit. It also makes a good spot for fortifications on the inside for your archers to shoot enemies at the edge or bottom of the pit.