Translation:There is a fountain in the middle of the city.
Well, there are more literal ways of saying city centre ("centro") and centre of the city ("centro da cidade") and so Duolingo may think "meio da cidade" should be translated differently. Also, and I don't know if this has any relevance here, the city centre is usually the centre of commercial activity which isn't necessarily located in the physical centre of the city. Perhaps, if you report it, Duolingo could be persuaded to accept your answer too.
"Middle" refers to somewhere away from the edge, as in "in the middle of the ocean" which is not really the geographic centre, but far from shore (Titanic sank in the middle of the Atlantic) or "I put my finger in the middle", which means somewhere near the centre. "Midst" on the other hand means "among", "in between", or "immersed in" such as "in the midst of the crowd", or "in the midst of all this confusion". Sorry I'm so late with my post!
Jonatha, I wonder where you got the idea that you actually NEED to use the word "midst" anywhere in English. It is an archaic term usually reserved for literature and idiomatic expressions like "There is a traitor in our midst" or "I'm in the midst of (doing something)". In day to day life, people normally use "in the middle of" or other expressions to convey the same meaning.
Hi Sylvain. I'm not able to remember where I've seen this word (midst) and why and when my doubt has started but it's nice to know that this word is archaic. In this case I can just forget it and focus in the more used word!! Because I use a variety of material to learn English, sometimes I find something wrong in its middle. (wow, after your explanation it's easier to apply the word lol). Sometimes I find or learn something that isn't exactly wrong, but is an archaic or not very used word and, as I have no contact with people who have English as a native language, I just realize that is an unusual word after somebody like you tells me. So, thank you for the elucidation and I hope you continue to make comments like that in order to help people like me whom are learning.
For a second I was afraid I was excessive in my statement, but apparently the Oxford dictionnary shares my view.
By the way, it is ok to be archaic as long as you got style doing it. ;)
Perhaps that dictionary should only describe "midst" as archaic when it is used as a preposition (the example sentences provided do indeed seem quite literary), but here "midst" would be used as a noun which is a different matter. Only the preposition is marked archaic in British English:
And "midst" seems to thrive in modern US media: http://tinyurl.com/h97d7vh
Even so, I agree that "middle" is a better fit in this sentence.