Krillion prompt · October 3, 2026
Name a type of structure built underground (man-made)
Krillion accepted 176 answers for this prompt in Dive #80. They’re all below, starting at the trench floor with the gems and rising to the Plankton everyone thinks of first.
Test a guess
Thinking of playing? Test a word before you look.
Notes on this prompt
- With 176 accepted answers, this prompt is narrower than a typical Krillion prompt (about 403), so there’s less room to go deep.
- 103 answers (59%) are Deep Cuts and 50 are Rare, while 6 sit at Plankton.
Quick picks
The shortest Rare or deeper answers, easy to type before the timer runs out.
Kiva +60 Qanat +60 Vault +60
Also accepted elsewhere
The same answer counted for a different prompt in the archive.
Every accepted answer
One in a Krillion
The gem picked for each prompt. Trench floor.
- Denehole
Chalk miners sank a narrow shaft, then hollowed out chambers below.
- Erdstall
A medieval tunnel network with tight squeezes and a still-debated purpose.
Deep Cut
Real obscurity. This is where the list gets long.
- Archive vault
- Artificial cave
- Auxiliary Units operational base
- Barabara
- Biogas digester
- Canal tunnel
- Catch basin
- Cist
- Columbarium
- Cryptoporticus
- Cycling tunnel
- Duct bank
- Earth lodge
- Flood tunnel
- Fogou
- Freight tunnel
- Geothermal well
- Ghost station
- Grease trap
- Hiding complex
- Hypocaust
- Hypogeum
- Infiltration gallery
- Inspection pit
- Leach field
- Mikveh
- Mithraeum
- Nilometer
- Ondol
- Ore pass
- Piles
- Pit latrine
- Pumped storage cavern
- Qargi
- Qarmaq
- ROC post
- Rock-cut church
- Rock-cut temple
- Rock-cut tomb
- Sardab
- Seismic vault
- Shaft tomb
- Slurry pit
- Soakaway
- Souterrain
- Stepwell
- Stope
- Storage cavern
- Stormwater tank
- Sump
- Sunken courtyard yaodong
- Sunken tandoor
- Tram tunnel
- Undercroft
- Underground aquarium
- Underground bathhouse
- Underground boiler room
- Underground bus station
- Underground cinema
- Underground dam
- Underground data centre
- Underground factory
- Underground farm
- Underground fortress
- Underground funicular
- Underground garden
- Underground granary
- Underground greenhouse
- Underground hangar
- Underground hospital
- Underground hotel
- Underground library
- Underground magazine
- Underground museum
- Underground nightclub
- Underground office
- Underground postal railway
- Underground power station
- Underground public toilet
- Underground pumping station
- Underground quarry
- Underground railway depot
- Underground reservoir
- Underground restaurant
- Underground sauna
- Underground school
- Underground sewage treatment plant
- Underground shooting range
- Underground sports hall
- Underground storage tank
- Underground street
- Underground submarine base
- Underground substation
- Underground telephone exchange
- Underground theatre
- Underground warehouse
- Underground water tank
- Underground water treatment plant
- Underground wind tunnel
- Utility vault
- Wheelhouse
- Wildlife tunnel
- Winze
Rare
Genuinely uncommon. A strong pick on any prompt.
- Aqueduct
- Borehole
- Burial vault
- Cave house
- Cellar dwelling
- Cesspit
- Cistern
- Crawl space
- Culvert
- Dugout
- Earth oven
- Earth-sheltered house
- Elevator shaft
- Escape tunnel
- Foundation
- Foxhole
- French drain
- Icehouse
- In-ground pool
- Kiva
- Manhole
- Military tunnel
- Mine tunnel
- Nuclear waste repository
- Oil well
- Ossuary
- Particle accelerator
- Pedestrian tunnel
- Pipeline
- Pit house
- Qanat
- Road tunnel
- Secret tunnel
- Seed vault
- Septic tank
- Smuggling tunnel
- Storm drain
- Sub-basement
- Trapping pit
- Trench
- Tunnel network
- Underground base
- Underground city
- Underground laboratory
- Underground mall
- Underpass
- Underwater tunnel
- Utility tunnel
- Vault
- Ventilation shaft
Schooler
Solid, but you’re swimming with the crowd.
- Bomb shelter
- Catacombs
- Cellar
- Crypt
- Dungeon
- Fallout shelter
- Missile silo
- Railway tunnel
- Root cellar
- Storm cellar
- Subway station
- Tomb
- Underground garage
- Well
- Wine cellar
Plankton
The first thing everyone thinks of.
- Basement
- Bunker
- Mine
- Sewer
- Subway
- Tunnel