Ginger-and-lemon syrup combines with seltzer for a refreshing drink.
Bring ginger, lemon peel, and 4 cups water to a boil in a medium saucepan over medium-high heat. Cook 10 minutes. Reduce heat to medium. Add sugar, and stir until it has dissolved. Return to a boil. Cook until syrup has been reduced to 2 cups, about 15 minutes.
Pour syrup through a fine sieve into an airtight container; discard ginger and lemon peel. Let cool slightly. Cover, and refrigerate until cold, at least 1 hour (up to 1 week). To serve, fill 8 glasses with ice and lemon slices if desired; stir 1/4 cup syrup and 1 cup seltzer into each glass.