In provincia. Così come i nomi di Regione non prendono MAI la preposizione articolata: IN Lombardia, IN Piemonte, IN Sicilia

Pay attention... The answer you chosed as the best is simply wrong :) It is all in the comment (if you needed a translation you should ask before), in my answer in this page and here : http://www.italki.com/answers/question/142189.htm

Here are further useful examples about the use of determinative article (and so about articulated preposition): http://grammatica-italiana.dossier.net/grammatica-italiana-06.htm The site is one among the best about grammar.