His works at Oper Frankfurt included Puccini's Madama Butterfly in 2001, Wagner's Tristan und Isolde in 2003 and the first production in German of Aulis Sallinen's Kullervo in 2011.

[1] His first plays were produced at the Theater Köln, including the first performance in Germany of Occupations (Roter Sonntag in Turin) by Trevor Griffiths in 1973.

[1] Nel collaborated in interdisciplinary and experimental work with Heiner Goebbels and William Forsythe at the Theater am Turm [de] Frankfurt.

[8] He staged Die Frau ohne Schatten by Richard Strauss,[8] and the first production in German of Aulis Sallinen's Kullervo in 2011.

[8][9] Nel directed world premieres, of Rolf Riehm's Das Schweigen der Sirenen at the Staatstheater Stuttgart in 1994, and of Mauricio Kagel's TheaterKonzert at the Deutsche Oper am Rhein in Duisburg,[8] as part of the 2003 Ruhrtriennale.