First, wash 5 limes, rub dry and peel thinly with a peeler. Peel fresh ginger and cut into thin slices.
Boil water with brown sugar, lime zest and ginger for 5 minutes over medium heat. Coarsely chop mint stems with leaves and add to lime-ginger broth and remove from heat. Let steep and cool for 3-4 hours.
In the meantime, squeeze the peeled limes and another 5 limes (200-220 ml juice).
Pour the ginger tea through a sieve and add the lime juice.
Fill glasses halfway with ice cubes and top with lime-ginger iced tea. Garnish with mint.