英文關鍵字
sewage
pipe
sewer
pollution
collector
drainage
stream
ecology
dirty
river
tunnel
environment
urban
pipeline
water
industrial
drain
flow
wastewater
danger
sewerage
tube
waste
channel
subterranean
flowing
nature
inside
deep
underground
dark
dirt
background
concrete
old
industry
contamination
city
environmental
mystery
chemical
contaminated
corridor
architecture
liquid
mud
canal