I wanted to write: "In the Hall of Mirrors." but stuck to room but "the" was wanted. I have reported both of Duos answers as incorrect. I wonder if all those who have recognized how bad they are have reported them. Many things have improved since I've been on Duo and reporting is one of the reasons.
Due's "correct" translation is wrong...
[IT] Siamo nella stanza degli specchi. = [EN] We are in the mirrors' room.
Or: [EN] "We are in the room of mirrors." (which is preferable to mirrors' room)
The little apostrophe following mirrors is important.
That is how one signifies possessive for words that end with the plural 's'.
(One can say "the mirror room". Mirror being singular.)
Those are the answers if Duo wants the literal translation.
Of course, Galleria degli Specchi ¹ is called "Hall of Mirrors" in English.
Whether one is learning Italian "from" English or English "from" Italian, it seems good for us to encounter difficult cases such as this one early, to increase one's caution about assuming one is making oneself clear. For what it's worth, what follows is everything I can think to say about talking in English about a room that contains mirrors.
If a room, one already known to both speaker and listener, were notable for containing one or more mirrors, I think we English speakers, or at least we American ones, would tend to refer to it as "the mirror room." In this construction, I don't think many of us would use the plural "mirrors", the possessive plural "mirrors'," or the participle "mirrored." But "the mirror room" has something of the feeling of an agreed proper name for a given room. In directing someone to an unfamiliar room that contains several mirrors, I think many of us would call it "the room with the mirrors." I think, "the room of mirrors" and "the room of the mirrors" sound as if they are agreed proper names: "the Room of Mirrors," "the Room of the Mirrors." Both sound elevated or formal.
Non native in English I thought The Hall of Mirrors i Versailles was called The room of mirrors. No garbage room: http://thisisversaillesmadame.blogspot.com/2013/03/hall-of-mirrors.html?m=1
I was on a computer doing Duolingo when a question appeared saying that I have to say something correct so I pressed the microphone to record what I was going to say and it said on the screen that I had to do something to be able to use the microphone but it seemed to hard so I pressed the skip button and it said I was wrong. I think that when those questions appear ( With the microphone) it should have a button that says Or is it too loud (Or something like that) and if you press it it skips over it without saying your wrong.