Sewer Lines

Under the houses, office building and streets pass the network of sewer lines.
These sealed pipes carry the stinky stuff that got flushed from the toilets plus other used water.

It goes to the place the clever engineers designed to process that toxic gunk.
Then when the processes had done their important job, the smells and poisons were removed.

Those buried sewer lines are our silent servants.

I (imagine that I can) see you there silent servants.