Mention "Pontine Islands" anywhere outside Italy, and you're likely to draw blank stares. The treasures of this archipelago -- inhabited Ponza and Ventotene plus the islands of Palmarola, Zannone, and Santo Stefano -- lie just far enough from a major port to have stayed under the radar of mass tourism. It takes 3 hours to reach Ponza from Rome, and 2 hours to reach Ventotene from Naples. Whenever an island is a bit of a pain to reach, it stays true to its roots. Outside of July and August, you'll find Ponza and Ventotene empty except for those who actually live there, and you'll be able to participate in their traditions and rhythms -- slow, relaxing, and insular being the keywords. In peak summer, there are slightly different traditions, involving a surge in population and the very ingrained social rites of the beautiful city folk who descend here en masse.
The Pontine Islands are somewhat arbitrarily grouped together; in fact, they consist of two distinct island groups, north and south. Ponza, Palmarola, and Zannone in the north are closer to Rome and geologically part of the mainland, while Ventotene and Santo Stefano in the south are closer to Naples, both in their red-tufa mineral makeup and their pastel architecture. It's an hour-long boat ride to cover the distance between Ponza and Ventotene.
Ponza is the largest and most populous of the group (though by no means big -- only 8 sq. km/3 sq. miles and with just over 3,000 permanent residents) and has the most tourist facilities. In July and August, it is the playground of moneyed Romans (especially) and Neapolitans (to a lesser extent). A geological marvel with all kinds of lunar volcanic rock, Ponza has spectacular and strange coves and beaches, and days are spent bobbing around the striking coastline in private yachts or rented gommoni. In the evenings, Ponza town is a pageant that involves everyone on the island; the portside walkway becomes a passerella (runway) on which vacationers flaunt their tans and carefully assembled-to-look-carefree island outfits. There is no shortage of aperitivo bars and waterfront restaurants at which to pursue or observe this behavior.
The de rigueur day trip from Ponza is boating over to the island of Palmarola (not served by the ferry companies); 10km (6 miles) to the west and all but uninhabited, it's the most naturally gorgeous of the Pontines, with coves straight out of a pirate movie and water a shade of emerald unique in the Mediterranean. Also an easy hop from Ponza is the nature reserve island of Zannone, which has shade (an important commodity in these islands) and panoramic hiking trails and rounds out the three islands of the "northern" Pontines.
Ventotene may be the main island of the southern Pontines, but it's a sleepy, wonderfully old-fashioned place that makes Ponza look like Manhattan by comparison. Ventotene is a tiny sliver of red volcanic stone capped by fertile land and fringed by intimate, mostly rocky coves. One of the most simple and delightful seaside villages in all of Italy is Ventotene town, built by the Bourbons of Naples in the 18th century. In antiquity, the Romans used Ventotene as a place to exile embarrassing imperial family members, and evocative ruins of their villas remain among overgrown prickly pear and agave plants. The Roman port of Ventotene is going strong after 2,000 years, harboring the fishing and tourism fleet of the island.
One nautical mile from Ventotene is the panettone-shaped islet of Santo Stefano, famous for its now-defunct prison, built in the late 18th century. Though the island is privately owned and the prison is not technically open to the public, Santo Stefano is easily visited with boatmen from Ventotene and home to a singular swimming opportunity in a Roman-era seawater "Jacuzzi" tub called the Vasca di Giulia.