One of my favorite book series is the 'SPQR' set by John Maddox Roberts

Numerous times the character makes mention of the smells, especially the bad smells(depending on the wind direction) that can be really bad.

What brings this up?  An article on how it smelled in ancient Rome,   Considering their major sewers ran straight into the Tiber, and that sometimes bodies were part of what was running out...  Yeah, I'd say 'bad'.  One whole book was about the sewers not having been properly maintained by previous officials and the consequences when the river flooded.

So that's what brought this to mind.