Hmm... Something of a DF noob here, but I think I may have stumbled upon something rather rare.
First, a little background, I guess... I started DF thanks to somehow getting to reading Boatmurdered... then Mermaid ranching... then Cacame. I wound up starting a game after drifting through the wiki for no less than three days, and genning several worlds.
I wasn't sure about what I wanted, so I just upped the vulcanism, and searched for pretty much everything.
On my last attempt before I would have given up, I got it.
Magma pipe, underground river (actually 7 stories above ground level), bottomless pit (and chasm if you make the embark wide), HFS (if you make embark wide), and on two biomes, split roughly 50/50. One is warm mirthful shrubland (unicorns) with sand, chalk, marble, and gabbro with plenty of magnetite. The other is a standard volcanic mountain with Andersite, Rhyolite, and Granite. Making your embark point wider and less "tall" will make you have more mountain and less shrubland.
This was already pretty spectacular, so I naturally decided to settle there, but then I found some other unusual stuff later on...
The first civ I would have gone with, the Soaked Pulley, was actually completely wiped out by the elves. My second choice, the Godly Tombs, actually had an elven queen (who was nothing but a farmer, no Cacame by any stretch). The elves are, strangely, actually conquering much of the world, which, it turns out, seems to be because the elven empire features a large number of goblins from some war where elves conquered goblin fortresses, and then started expanding rapidly. One of the goblin empires, meanwhile, feature literally more humans and elves in their forces than actual goblins, and one that I embarked on top of to see actually had elven priestesses and a legendary spearelf.
I've also had over 30 dwarves migrate every Spring (36 last time) except the first spring's migration, which was "only" 18. (I guess they want to flee elven rulership?)
Anyway, I'm five years into my fortress, although I have backup saves for different years so that I could view my annual progress. The biggest problem with this place is that the magma vent (and the pit) are kind of far from the rest of the features. You need to make embark 7x, 4y to make the underground river and magma vent both fit in the same embark, and HFS requires 8x and 5y. I've managed to dig my magma channels (the magma vent is right in the middle of the sand, so easy glass production there), but have yet to really get my water tower tapped and my massive resevoirs going. It's height makes pressurizing water extremely easy, and I think I'm going to dig a massive vertical chamber using all 22 elevations near the start of the river so that I have a "Pressurized Water Tower" that can supply water to the rest of the fort.
The underground river is, as I said, seven elevations above the shrubland ground level, and appears as a waterfall apparently from another dimension only a couple z-levels from the peak of the mountain, so it would actually be fairly easy to flood the (non-mountain) world, if it weren't for the open-air magma vent and bottomless pit.
Worldgen data (note I ham-handedly forced more vulcanism):
Created in DF v0.28.181.40d.
[WORLD_GEN]
[TITLE:PLAYGROUND]
[SEED:3620778183]
[HISTORY_SEED:941002251]
[NAME_SEED:245258356]
[DIM:129:129]
[END_YEAR:1050]
[BEAST_END_YEAR:200:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:401:401]
[RAINFALL:0:100:200:200]
[TEMPERATURE:25:75:200:200]
[DRAINAGE:0:100:200:200]
[VOLCANISM:0:100:200:200]
[SAVAGERY:0:100:200:200]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[GOOD_SQ_COUNTS:25:251:503]
[EVIL_SQ_COUNTS:25:251:503]
[PEAK_NUMBER_MIN:12]
[OCEAN_EDGE_MIN:2]
[VOLCANO_MIN:33]
[REGION_COUNTS:SWAMP:260:1:1]
[REGION_COUNTS:DESERT:260:1:1]
[REGION_COUNTS:FOREST:1040:3:3]
[REGION_COUNTS:MOUNTAINS:2080:2:2]
[REGION_COUNTS:OCEAN:2080:1:1]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:2080:3:3]
[REGION_COUNTS:HILLS:2080:3:3]
[EROSION_CYCLE_COUNT:250]
[RIVER_MINS:100:100]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:25]
[NON_MOUNTAIN_CAVE_MIN:50]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_RIVER:2]
[SHOW_EMBARK_POOL:2]
[SHOW_EMBARK_M_POOL:2]
[SHOW_EMBARK_M_PIPE:2]
[SHOW_EMBARK_CHASM:2]
[SHOW_EMBARK_PIT:2]
[SHOW_EMBARK_OTHER:2]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:20]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:2080:4160:2080]
[RAIN_RANGES:2080:4160:2080]
[DRAINAGE_RANGES:2080:4160:2080]
[SAVAGERY_RANGES:2080:4160:2080]
[VOLCANISM_RANGES:2080:4160:4196]
Where to find the site:
I'd post one of those pictures of the entire map, but I can't remember what I'm supposed to press to generate one of those.
Anyway, I'm just wondering how odd all these things are... I know the oddest thing to me when I started was just how many dwarves came each Spring, but I'm getting the impression I really, REALLY lucked out on worldgen, and have a very unusual world history, considering how the elves have so much land.