Mljet National Park

Mljet National Park covers the western third of Mljet Island, roughly an hour by boat from Dubrovnik. It's Croatia's oldest protected marine area, established in 1960, and still one of the quietest corners of the southern Adriatic.

The park's signature feature is a pair of saltwater lakes connected to the sea by narrow channels: Veliko Jezero (Great Lake), which reaches depths of 46 meters, and the smaller, shallower Malo Jezero. On an islet inside Veliko Jezero sits a 12th-century Benedictine monastery, now a café, which is the most-visited spot in the park. Because the lake water mixes with the sea through those narrow passages, it warms up faster than the open Adriatic — which is why people keep swimming here even outside peak summer.

The park is also home to the only coral reef in Croatia: a bed of sod coral (Cladocora caespitosa) growing in Veliko Jezero, one of the largest colonies of its kind in the Mediterranean.

Two villages, Polače and Pomena, serve as the main entry points, both with kiosks selling park tickets. From Polače it's about a 40-minute walk through pine woods to reach the lakes; from Pomena it's closer to 20 minutes to the small bridge (Mali Most) where boats cross over to the monastery islet.

For anyone chartering a boat in this part of Croatia, Mljet National Park is one of the anchorages you'll visit on a private gulet charter from Dubrovnik, usually paired with Korčula or the Elaphiti Islands on longer itineraries.