The phrase "an unprecedented sight" is correct and usable in written English.
It can be used to describe something that has never been seen before or is unique in its occurrence.
Example: "The solar eclipse was an unprecedented sight that left everyone in awe."
Alternatives: "a never-before-seen view" or "an extraordinary spectacle".
At Brisbane, we saw the unprecedented sight of 500 for one as England attained that total of runs and wickets on its way to a match-saving 517 for 1.
So in 2013 Brazilians should be treated to an unprecedented sight: well-connected politicos behind bars.
Together with spouses and children they sauntered down São Paulo's Avenida Faria Lima, a thoroughfare conveniently located close to many of their offices.It was a sight to behold perhaps unprecedented in election history, and not just in Brazil.
And yesterday there was the possibly unprecedented sight of an international coach, Jamie Siddons, berating the shot-selection of his own captain, Mohammad Ashraful, while his captain was sitting head bowed to his left.
While they remain strong and well-resourced, there have been unprecedented sights.
The end of the season this year brought at least one unprecedented sight.
The people to whom he is referring are presumably not the ones who will pack Coors Field on Saturday night to witness the unprecedented sight of late October baseball in Colorado and the first World Series game to be played at such a high altitude.
And what happened as you point out, well the French happened, as Secretary Kerry concluded marathon talks directly with Iranian officials, unprecedented sight there really.
The virtually unprecedented sight of members of the legislative branch of U.S. government trying with little success to enforce orders from the judicial branch against the will of the executive branch has already prompted some to suggest that Trump's executive order is sparking a constitutional crisis.
