According to this Spanish-language article, Romanians are now the biggest foreign population in 12 out of the city’s 21 districts.

Here’s the breakdown of the biggest foreign resident population by district:

Center – Italian
Arganzuela – Chinese
Retiro – Romanian
Salamanca – Italian
Chamartin – Paraguayan
Tetuan – Filipino
Chamberi – Italian
Fuencarral-Pardo – Romanian
Moncloa-Aravaca – Romanian
Latina – Romanian
Carabanchel – Romanian
Usera – Chinese
Puente Vallecas – Romanian
Moratalaz – Romanian
Ciudad Lineal – Colombian
Hortaleza – French
Villaverde – Romanian
Villa de Vallecas – Romanian
Vicalvaro – Romanian
San Blas – Romanian
Barajas – Romanian

And in three of the districts, Romanians are the second most populous foreign group.

Madrid has a population of about 3.5 million people and it is estimated that about 1 in 5 residents are foreigners.