Ilkay Gündoğan traveled to Barcelona on Monday according to a report in the German newspaper Bild.
While the reason for the trip is unknown, the Catalan club have been linked with the German international midfielder in recent weeks.
However, Barcelona cannot sign Gündoğan this summer due to a transfer suspension and would have to wait until January 2016.
Barça Blaugranes have stated that talks with Gündoğan have reached an advanced stage but there is still disagreement over the transfer fee.
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Dortmund are reported to be asking for €40 million but Barcelona do not want to go above €32 million.
Both Arsenal and Manchester United have also been closely linked with the 24-year-old over the past week according to the Daily Mail.
The Dortmund star is also reported to have attracted interest from Manchester City according to the Manchester Evening News.
Gündoğan has four assists and three goals in 30 appearances for Dortmund this season.
