Using a vegetable peeler, remove the peel from the lemons in long strips (reserve the lemons for another use).
Place the lemon peels in a 2-quart pitcher. Pour the vodka over the lemon peels, cover and steep for 4 to 5 days at room temperature.
Heat the water and sugar in a large saucepan over medium heat until the sugar dissolves and makes a syrup. Cool completely. Pour the sugar syrup into the vodka mixture.
Let stand at room temperature overnight. Strain limoncello into bottle, discarding the peels. Add additional decorative peels to bottle, seal and refrigerate until cold, at least 4 hours and up to 1 month.
Yield: 2 quarts