At a mercifully-unnamed diner, Mike Pailliotet professionally cleans some truly nasty carpet: low-pile commercial standard at a stage far beyond gross. It's been transformed into a rubbery, slightly shiny mat of congealed grease.
"We live in a primitive time, don't we, Will? Neither savage nor wise. Any rational society would either ban carpet in diners or let me take my dog in there." — Hannibal Lecter.
Here's another delight from Pailliotet's channel, titled "Manky Urine Filled Carpet Cleaning Fail – See The Funk That Hides In Carpeting." The delights are revealed about 6m30s in.
Mikey has forums you can visit at his website if you're interested in the wonderful world of carpet cleaning. See also the TruckMount forums for more on how useless consumer-grade carpet cleaners are; the Zipper cleaning wand alone that Mikey uses is more than two grand.