My favorite for years: Geschwindigkeitsbegrenzung
First time I saw that work my mind gear-jammed.
Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz -
63 words long - a law describing the regulation of beef labeling! Considered satirical even by native German speakers.
Since repealed.
“Geschwindigkeitsbegrenzung”
Never saw that word when I was in Germany because then there were NO speed limits!
Now, “Polizei” and “Strafsbefel” were words I knew well.
;^)