I've found a rather enjoyable location, so I thought I'd share it. It is a major river and minor river in one very compact location.
The major river, called The Droplets of Odor, is 47 tiles wide! There is a 10-z-level waterfall
on the major river!
The river is level to the plateau (accessible) before the waterfall, and drops down between sheer cliff faces!
The land all around is generally rough and rugged too, with significant hills and valleys, and a few ponds.
There is a subterranean magma vent north of the major river, in that smooth spot west of the minor river.
There are a good many trees and there is plenty of yellow sand.
The only aquifer I've encountered is to the south of the river. It's only one z-level deep, and it's a few layers down.
And to make it even better, the whole thing freezes during the winter! Stays frozen for the better part of it, too!
You can get it all in a 2x2 if you want. I used a 3x3.
If you extend a few tiles west, I think there's an obsidian layer and black sand in that broadleaf biome.
There's an elvish camp nearby, which is enticing given the availability of large amounts of water/magma.
But it's pretty far away to really be worth it. There's a lot of empty, boring forest in between.
Here are the world gen parameters:
[TITLE:EPIC]
[CUSTOM_NAME:The World]
[SEED:4213020133]
[HISTORY_SEED:3673399100]
[NAME_SEED:491298722]
[DIM:257:257]
[END_YEAR:10000]
[BEAST_END_YEAR:99:0]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:1:400:800:800]
[RAINFALL:0:90:400:400]
[TEMPERATURE:20:80:400:400]
[DRAINAGE:0:100:400:400]
[VOLCANISM:10:100:400:400]
[SAVAGERY:0:100:400:400]
[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:200:0:0]
[EVIL_SQ_COUNTS:300:0:0]
[PEAK_NUMBER_MIN:10]
[OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:60]
[REGION_COUNTS:SWAMP:1032:7:6]
[REGION_COUNTS:DESERT:1800:12:11]
[REGION_COUNTS:FOREST:3500:12:11]
[REGION_COUNTS:MOUNTAINS:9000:18:17]
[REGION_COUNTS:OCEAN:8256:7:6]
[REGION_COUNTS:GLACIER:200:1:0]
[REGION_COUNTS:TUNDRA:800:1:0]
[REGION_COUNTS:GRASSLAND:8256:13:12]
[REGION_COUNTS:HILLS:8256:13:12]
[EROSION_CYCLE_COUNT:250]
[RIVER_MINS:400:400]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVE_MIN_SIZE:1]
[CAVE_MAX_SIZE:500]
[MOUNTAIN_CAVE_MIN:30]
[NON_MOUNTAIN_CAVE_MIN:30]
[ALL_CAVES_VISIBLE:1]
[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:30]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:8256:16512:8256]
[RAIN_RANGES:8256:16512:8256]
[DRAINAGE_RANGES:8256:16512:8256]
[SAVAGERY_RANGES:8256:16512:8256]
[VOLCANISM_RANGES:8256:16512:8256]
(Don't let END_YEAR:10000 throw you off. It stops at 99)
And here's the embark location I used:
The only mods I use are simple creature-adds I made myself. Llamas, falcons, and the cat bug fix.
I don't think those would make a difference in world generation. I hope I am correct.
I'm really not sure if this is anything special. It's the first major river I've ever embarked on.
But I believe that waterfalls (and rough terrain in general) are hard to come by on really nice rivers.
Let me know what you think!