On Subterranean Landscapes

Now that I'm firmly ensconced in writing about the Underworld, it behooved me to put some thought into landscapes deep beneath the surface of the earth. To that end, I dashed out some ideas to work off of - and will probably add to it as I go. Of course, these are fantastic landscapes, so take them with a grain of salt. Maybe they'll be useful to some other world builders out there.

Profile
- Circle
- Oval (fat or tall)
- Square
- Rectangle(fat or tall)
- Diamond
- Hexagonal

Character of the Walls/Ceiling
- Ledges (wide, narrow, steep, gentle)
- Pocked with cave opening or openings (ground level, high, how many?, uninhabited, abandoned, inhabited by animal life or sentient life?)
- Waterfalls pouring from the walls/ceiling- Lava flowing from the walls/ceiling
- Smooth and hard to climb
- Damp and slimy
- Hot to the touch (lava flows behind them?)
- Carved (art, cliff dwellings, stairs or ladders to caves, mines, rent by claws)
- Glowing (phosphorescent fungus or minerals, radiation, magic)

Character of the Floor
- Canyons / badlands
- Ridges (blunt, razor-sharp obsidian)
- Mounds- Stalactites (massive) – stalagmites above presumably
- Sandy
- Pebbled / rocky
- Smooth and flat
- Wet and slippery – myriad of streamlets
- Subterranean river (slow and lazy with inhabitants on banks, torrential, glacial)
- Underground lake (fed by streams or a spring)- Sharp incline- Sharp decline
- Very low ceiling (6d6 feet)
- Sinkholes (karst topography)
- Geysers / steam vents / gas vents
- Chasm (stream or lava or sand or quicksand or spikes or poison gas at bottom, inhabited by giant monster or small monsters)
- Strewn with bones (fell from above, remains of battle, remains of large predator's hunt)
- Pools or lakes (clear and clean water, hot springs with mineral salts, brackish and slimy, saline water, mild or powerful acid, magical, mercury)

Character of the Air
- Damp and chill - misty
- Damp and warm - steamy
- Dry and chill
- Dry and warm
- Hot (volcanic activity involved, or magic)
- Frigid
- Smoky and acrid
- Acidic tang to the air
- Smell of rot and decay
- Cacaphony of animal or monster noises
- Sound of running water
- Rumble of geological activity
- Windy (gentle, powerful, vortex/tornado)

Resources
- Fungal fields (requires water or damp air and animal fuel)
o Slimes (ooze encounters likely)
o Mushrooms (small) (chance of mushroom monsters)
o Mushrooms (large) (chance of mushroom monsters)
o Algae
o Moss
o Bacterial soup (primordial ooze) (ooze encounters likely)
o 20% chance of grazers
o 1% chance of sentient creatures – farmstead

- Animals (probably requires fungal fields)
o Bats
o Cave fish or eels
o Moles
o Cave salamanders
o Cave crickets
o Shrimp
o Cave beetles
o Cave crayfish
o Silverfish
o Isopods
o Cave snail
o Velvet worms
o Cave wolf spider
o Harvestman spider
o Eyeless albino millipede
o Cave sandhopper
o Beauty rat snake
o Mole rats (good source of intelligent species based on Rufus)
o Note – troglobite creatures have heightened senses (hearing, touch, smell), lack of pigment and eyesight, lack of wings and longer appendages in insects)

- Minerals or Gases

If you have any bright ideas to add to this list, I'd love to hear them!

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Image by Dave Bunnel, found at Wikipedia