Minturno War Cemetry is an important piece of the area's history. Keep an eye out for any epitaphs which often reveal many illuminating facts.
You're spoiled for sightseeing choice in Nettuno. Minturno War Cemetry is a great place to begin here, but there are lots of other worthwhile spots to check out. Sanctuary of Madonna delle Grazie and Santa Maria Goretti, Grotte di Nerone, and Imperial Villa of Nerone are near the burial ground and will top off your day nicely.