In a small saucepan, bring water and sugar to a boil. Reduce heat; cover and simmer for 5 minutes. Remove from the heat; stir in the mint, lemon juice, orange juice and zest. Cover and let stand for 1 hour.
Strain and discard mint and orange peel. Stir in cold water; serve over ice. Garnish with lemon slices and additional mint if desired.