Other than the beach – and great views from the historic centre – Sperlonga's main attraction is this seafront archaeological museum. Here you can admire striking ancient sculpture, including a muscular depiction of the cyclops Polyphemus being blinded, and poke around the ruins of Villa Tiberio, the Emperor Tiberius' waterfront villa set around a gaping sea cave.
The museum is south of town, off the main coastal road, Via Flacca (SS123). On foot it's a 1.5km walk from the small marina on the southern side of the centro storico.