Nisa is a municipality in Portalegre District in Portugal. The population in 2011 was 7,450, in an area of 575.68 km. The present Mayor is Mariā¦Nisa is a municipality in Portalegre District in Portugal. The population in 2011 was 7,450, in an area of 575.68 km. The present Mayor is Maria Idalina Alves Trindade. The municipal holiday is Easter Monday.