Less widely known than the Saturnia Hot Springs, the free-to-access Petriolo Thermal Baths are public; set between two nature reserves; and sit next to a small river, making them ideal for hot and cold plunges. Find the baths off the main road between Siena and Grosseto: watch for signage, look out for a stone bridge, and park near the ruins of an ancient wall. Monticiano is the nearest town, but travelers can soak sore muscles here after hiking or wine-tasting trips from Siena.

With deep pools, cascading waterfalls, and emerald waters, the Torrente Fer (torrente means “torrent” or “cascade” in Italian) is popular among canyoners but also has swimming holes rivaling northern Italy’s best. The cascade is next to the Dora Bàltea River in the Aosta Valley, a small region in northwest Italy known for Parco Nazionale Gran Paradiso, one of the best-known parks in Italy. While some pools get crowded during summer, it’s just a short hike to the more secluded upper pools.

These natural pools formed by the Meduna River are inside the Friulian Dolomites Nature Park (Parco Naturale Dolomiti Friulane), roughly 2.5 hours north of Venice by car. Surrounded by forests and boulders, they’re considered one of Italy’s wildest swimming spots. The nearest village is Tramonti di Sopra, but the pools are in the heart of a remote region, surrounded by multiple national parks, the nearest being Dolomiti Bellunesi National Park (Parco Nazionale delle Dolomiti Bellunesi).

Seven swimmable coves lie along the shoreline of the Zingaro Nature Reserve, a protected area laced with marvelous paths to the sea. Sicily’s first nature reserve, it’s located one hour west of Palermo by car—the southern entrance is just past the Tonnara di Scoppelo, a medieval tuna fishery-turned-museum and public beach. Reach the coves from the water on a boat tour of the reserve and neighboring San Vito lo Capo; spend a day biking the area; or admire it from the medieval town of Erice.

This beach within the Monte Conero Regional Park (Parco Regionale Naturale del Conero) is accessible only by sea. One of Italy’s most remote beaches, it was recently christened the most beautiful, winning out for water quality, cleanliness, and surrounding beauty. Reach the “two sisters” on kayaks rented from San Michele Beach (Spiaggia di San Michele) or by the ferry service from Numana. Otherwise, paddle out with a tour group, sail the neighboring coastline, or hike to Mount Conero.

At the tip of Sicily’s Cape Milazzo, a secluded path leads past olive groves, ruined watchtowers, and lighthouses to the Pool of Venus, a seawater pool protected on three sides by a rocky inlet. Though relatively small, the pool is isolated and especially beautiful during sunset. Locals take travelers on fishing trips in the surrounding waters, while visitors can stop for a dip before cruising out to the Aeolian Islands from the town of Milazzo.

In northeast Sardinia, on Mount Nieddu above San Teodoro, the Rio Petrisconi feeds a series of large granite pools that seem purpose-built for canyoning. The largest of these called the “infinity” pool, takes swimmers to a cliff overlooking a waterfall. There isn’t a wilder swimming spot in all of Sardinia, a region already known its out-of-this-world beaches. Nearby, explore Marina di Orosei, a beach with golden sand and crystal-clear waters, a perfect oasis for surfers and divers.

Though not “wild,” Gaiola Island makes our list for offering travelers the chance to swim among submerged Roman ruins. Just ahead of Naples' Virgiliano Park (Parco Virgiliano), the Discesa Gaiola descends toward Gaiola Beach—from there it’s a short swim through the Gaiola Underwater Park (Area Marina Protetta Parco Sommerso di Gaiola) to the island. While locals swim and snorkel here nearly year-round, travelers can kayak along the coast or explore the nearby Pausilypon Archeological Park.