Assuming you mean the Opera Garnier, the original 19th century opera house north of the Champs Elysees, you can take the RER regional rail line "B" into Paris, and change at Chatelet to the "A" line which stops at the Opera station.http://parisbytrain.com/wp-content/uploads/2008/05/metro120x84.pdf
Assuming you mean the Opera Garnier, the original 19th century opera house north of the Champs Elysees, you can take the RER regional rail line "B" into Paris, and change at Chatelet to the "A" line which stops at the Opera station.http://parisbytrain.com/wp-content/uploads/2008/05/metro120x84.pdf