Dr. Linden has been working as a lawyer since 1974. He is admitted in Germany. He manages the UTF branch in Aachen. Dr. Linden was mayor of the city of Aachen from 1984 to 1989. From 1989 to 2009 he was Lord Mayor of the city of Aachen.
After becoming a member of the Direktorium zur Verleihung des Internationalen Karlspreises in 1989, Dr. Linden became the chairman of the board of directors in 2009. This organization awarded the nationally and internationally renowned Charlemagne Prize to Aachen.
From 2001 to 2009 Dr. Linden has been an active member of the Presidium of the German Association of Cities. Further, He was a member of Aachen’s city council from 1997 to 2009. Dr. Linden is honorary citizen of the Euroregion Aachen, Heerlen, Liege and Hasselt, as well as honorary citizen of the European Academy of Science in Salzburg. He was awarded the Golden Medal of Honor of the Dutch city of Maastricht. He is the bearer of the French Order Grand Officier of the Ordre national du Merite.