I've read in some topic before that someone had an adamantine spire on embark...same story, very bad lag when generating the embark, "section of the cavern collapsed"...
...but in addition to the splendorous adamantine spire I also have plenty of sky magma and some semi-molten rock as a bonus which reaches the top of the spire!
Of course it all started falling on my embark as soon as it generated...
Anyone fancy the worldgen parameters? Didn't try to generate the world again, so no idea whether it'll produce the same wonders...
Created in DF v0.34.01.
[WORLD_GEN]
[TITLE:CREATE WORLD NOW = 4333333]
[SEED:TdG8G6U6ZsEjIzBgAMvv]
[HISTORY_SEED:H53E8ynEpu3FwekVrNrG]
[NAME_SEED:AWJ0Pr3ILsOyTcg4jzzr]
[CREATURE_SEED:nrhFLlPu9sQMkcF0CPmz]
[DIM:129:129]
[EMBARK_POINTS:1274]
[END_YEAR:250]
[BEAST_END_YEAR:250:-1]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:1600:1600]
[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:4:2:0:1:0:1]
[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]
[MINERAL_SCARCITY:2500]
[MEGABEAST_CAP:18]
[SEMIMEGABEAST_CAP:37]
[TITAN_NUMBER:9]
[TITAN_ATTACK_TRIGGER:80:0:100000]
[DEMON_NUMBER:28]
[NIGHT_TROLL_NUMBER:14]
[BOGEYMAN_NUMBER:14]
[VAMPIRE_NUMBER:14]
[WEREBEAST_NUMBER:14]
[SECRET_NUMBER:28]
[REGIONAL_INTERACTION_NUMBER:28]
[DISTURBANCE_INTERACTION_NUMBER:28]
[EVIL_CLOUD_NUMBER:14]
[EVIL_RAIN_NUMBER:14]
[GOOD_SQ_COUNTS:6:63:0]
[EVIL_SQ_COUNTS:6:63:0]
[PEAK_NUMBER_MIN:3]
[PARTIAL_OCEAN_EDGE_MIN:0]
[COMPLETE_OCEAN_EDGE_MIN:4]
[VOLCANO_MIN:1]
[REGION_COUNTS:SWAMP:66:0:0]
[REGION_COUNTS:DESERT:66:0:0]
[REGION_COUNTS:FOREST:264:0:0]
[REGION_COUNTS:MOUNTAINS:528:0:0]
[REGION_COUNTS:OCEAN:528:0:0]
[REGION_COUNTS:GLACIER:16:0:0]
[REGION_COUNTS:TUNDRA:33:0:0]
[REGION_COUNTS:GRASSLAND:528:0:0]
[REGION_COUNTS:HILLS:528:0:0]
[EROSION_CYCLE_COUNT:250]
[RIVER_MINS:25:25]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:0]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:100]
[CAVERN_LAYER_WATER_MIN:0]
[CAVERN_LAYER_WATER_MAX:100]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:15]
[LEVELS_ABOVE_LAYER_1:5]
[LEVELS_ABOVE_LAYER_2:1]
[LEVELS_ABOVE_LAYER_3:1]
[LEVELS_ABOVE_LAYER_4:1]
[LEVELS_ABOVE_LAYER_5:2]
[LEVELS_AT_BOTTOM:1]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:10]
[NON_MOUNTAIN_CAVE_MIN:15]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:40]
[TOTAL_CIV_POPULATION:15000]
[SITE_CAP:1040]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:8000:1056:528]
[RAIN_RANGES:528:1056:528]
[DRAINAGE_RANGES:528:1056:528]
[SAVAGERY_RANGES:528:1056:528]
[VOLCANISM_RANGES:528:1056:528]
Also my embark was here: