Mljet National Park

If the Elaphiti islands are the easy half-day escape from Dubrovnik, Mljet is the full day that people remember. The western third of this long, forested island has been a national park since 1960, and its centrepiece is a pair of saltwater lakes, the Great Lake and the Small Lake (Veliko and Malo jezero), linked to the open sea by a narrow channel and to each other by a shallow strait with a small bridge. The water is clear, sheltered and usually a few degrees warmer than the sea outside, and the lake shores are lined with Aleppo pine and holm oak that come right down to the rocks. In the middle of the Great Lake sits the islet of St Mary, with a twelfth-century Benedictine monastery and church that you reach by the park boat. The park entrance ticket is the practical key to the day: it includes one return boat crossing to St Mary, the marked trails around both lakes and up to the Montokuc and Veliki gradac lookouts, the forest path between the Small Lake and Pomena, parking at Vrbovica and, in summer, the little electric train. You arrive either at Polače, a village built into the ruins of a large late Roman palace, or at Pomena on the western tip, and from either the lakes are a short walk or shuttle away. Local legend makes Mljet the island of Calypso, where Odysseus was held for seven years, and there is a sea cave on the south coast that carries the name. The honest frame: Mljet is not a sight to tick off but a place to slow down in, and it rewards people who walk, swim, cycle or kayak rather than those who want a guided commentary.

Getting there is the part to plan. In season, fast passenger catamarans run from Gruž harbour in Dubrovnik to Mljet, and many travellers simply join an organised day trip that bundles the boat, park ticket and a lunch stop. Independent travellers get more flexibility: take the morning catamaran, buy the park ticket at the entrance (adult, child and student tickets bought in the park are cheaper after four in the afternoon), rent a bicycle or kayak at the lake edge in summer, and loop the Great Lake on the flat lakeside path before taking the boat to St Mary for lunch and a swim off the monastery jetty. A second return boat trip to the islet costs a small extra fee. Outside the summer months the boat timetables thin out and the island is very quiet, so check the current schedule before you go and allow for the possibility that the return crossing is earlier than you would like.

The walking is gentle and the reward is the light. The circuit of the Small Lake takes less than an hour, the full lakeside loop longer, and the climb to the Montokuc viewpoint gives a view across the lakes, the Pelješac peninsula and, on clear days, the open Adriatic. Swimming is allowed in the lakes and the bridge at the strait between them is the classic spot, with a gentle current that you can float with. In Polače, give twenty minutes to the Roman palace ruins and the remains of an early Christian basilica on the slope behind the harbour. Bring water and snacks if you are heading onto the trails, because cafes cluster at Pomena, Polače and the bridge.

Who should go: couples who want a day of nature after the crowds of the Old Town, families with children who can walk a few kilometres and love swimming, and anyone staying four nights or more in Dubrovnik. If you have only two days in the city, prioritise the walls and Lokrum instead. Mljet also makes a superb overnight, with small guesthouses in Pomena and Polače, and a night there lets you see the lakes empty in the early morning, which is when the island is at its most magical.