Where is the u21 euro championships being held?
Spain are the reigning champions, defeating Germany 2–1 in the 2019 final. The finals of the 2019 competition were hosted by Italy.
Where is the UEFA European U-21 Championship being held in 2019?
Italy
UEFA European Under-21 Championship
No context provided
Where was the UEFA European U-21 Championship held in 2017?
Poland
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Where was the UEFA European U-21 Championship held in 2015?
Czech Republic
UEFA European Under-21 Championship
https://en.wikipedia.org/wiki/UEFA%20European%20Under-21%20Championship
The UEFA European Under-21 Championship is a biennial football competition contested by the European men's under-21 national teams of the UEFA member associations. 
UEFA European Under-21 Championship
The biennial football competition, UEFA European Under-21 Championship has been held in Czech Republic (2015), Poland (2017) and in Italy (2019).