"An avenue is a very wide road."
Translation:Aleja to bardzo szeroka droga.
Also applies in parts of the USA. In Manhattan, NYC, "Avenues" run (approximately) North-South, and "Streets" East-West. This undoubtedly differs by city.
Fun fact - Milton Keynes, near to where I work, has numbered "V" roads and "H" roads which (approximately) behave the same as Manhattan's "Avenues" and "Streets".
("Vertical" and "horizontal", respectively)
Jellei, you won't be surprised that I was surprised that Duo rejected "Aleja to bardzo szeroka ulica". (I wrote about road vs. street in another thread.)
To an Englishman living in Germany, Duo's English sentence is ... confusing. My definition would be: "An avenue is a road lined by trees" ("Eine Allee ist eine von Bäumen umrandete Straße"). There were many such main roads in East Germany (former GDR) before they were widened after German unification to improve traffic flow.