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I am a Indian citizen going to Portugal from India with a Schengen visa issued by Portugal. I am travelling on the sponsorship of my friend in Portugal and have to change flight at Paris with a layover time of 13 hours. Do i need any transit visa for the Paris transit city tour at CDG airport? Also i want to take another tour of Paris while returning to India from Portugal. I will be having a layover time of 13 hours at Paris while returning also.