Hey!
I don't know if this has been discussed before but if it has, it is very difficult to find.
For the next fort, I want savage evil (terrifying) surroundings. The last time I did this, I got run over by undead elephants ten minutes into the game. So now I want "to seal myself off", if that is the right term. Did out a meeting hall and stockpile, get everything inside and then build a wall in front of the entrance.
Is it possible to survive without any contant with the outside world? And what would I want to embark with? I plan to make booze and food from plump helmets, the mud will come from a murky pool that I will afterwards seal with a wall. I assume wood will become a major problem though, I need it for beds.
It's possible, or rather, it's my favorite strategy. But you really need to get the migrants and merchants in if they can get past the goblin tower and other siegers. I usually wall-in just for the first year, getting a more sophisticated system in place by then:
Long corridors to map edges (with bridges and other means to control use) often help in this by giving migrants an underground passage via old mine shafts. I've played one walled-in scenario for 5 years with no immigrants and it sucked. Death just creeps in by other means and with no births. -> Fortress is doomed. In my case my dorfs were done in by fey moods or accidents.
I've played a lot of sinister/evil right-by-goblintower scenarios and I'd recommend building a ramp/wall with a bridge to allow entry into a walled space with cage traps, followed by a second ramp/bridge combo and floodgate & door. Preferably so that you can flood away any stuff that is jamming weapons traps and the bridges or blocking the doors and with fortifications 1z up from where you can shoot at stuff in the cage-arena. Optionally also arrange for drowning invaders.
Takes time and care to do this properly, but after this you can be pretty secure in any environment as long as you don't let any of your dwarfs go outside. this scaredy-cat strategy often leads to undertrained and inexperienced military, which will cause a lot of problems later on. Therefore it's important to get goblins in cages and dump them into execution arena for some military training.
Also, instead of just walling in, this way you can let things like migrants and traders in and catch some megabeasts and prisoners to target practice on.
Biggest problem with this setup is the jamming of bridges and doors/floodgates and their breakups. Try to avoid killing gobs on bridges. Using naturally carved areas, steep areas, for projects such as this, such as riverbeds (brooks that you can walk on) work very nicely as you can have multiple bridge systems and cage areas to que in the gobs or just have them directed to a different, special arena if no trolls came along.