Lush parks shaded by Roman pines and stately cypresses are familiar fixtures on the Italian landscape, but few of these retreats are as immaculately kept, as tranquil , and as simply lovely as the grounds of the Sicily-Rome American Cemetery in the seaside town of Nettuno, 38 miles south of Rome. Only birdsong and the sound of splashing fountains intrude on the contemplative silence of these 77 acres, where white crosses are arranged in gracefully curving rows to mark the graves of World War II service members who died in Allied landings and the fierce battles that led to the liberation of Italy.