6 lemons
2 stalk rhubarb, cut into 1-inch pieces
1 C. sugar
4 C. water

Using a vegetable peeler, peel zest from 4 lemons. Squeeze juice from peeled and remaining lemons to measure 1 C. Combine rhubarb, lemon zest, sugar and 2 C. water in saucepan. Bring to a boil, stirring, until sugar is dissolved and rhubarb is very tender. Strain mixture through a sieve; add lemon juice, then chill thoroughly. When ready to serve, pour mixture into pitcher. Add remaining 2 C. water. Pour over ice and garnish with lemon slices.