1. Mljet Island is a beautiful, forested island located in the Adriatic Sea, just off the coast of Dubrovnik. It is known for its stunning national park, which covers the western part of the island and contains two saltwater lakes - Veliko and Malo Jezero. The island is also full of ancient ruins, including the remains of a Roman palace and a Benedictine monastery. Mljet has a rich history and has been inhabited since ancient times.

2. The working time and phone number for Mljet Island’s national park can be found on their official website: https://www.np-mljet.hr/en/. The park is open year-round, with different hours depending on the season.

3. To reach Mljet Island, visitors can take a ferry from Dubrovnik or other nearby towns. Tickets can be purchased at the ferry terminal or online through various ticketing websites. Once on the island, visitors must purchase a ticket to enter the national park, which includes access to the lakes and other attractions. The cost of tickets varies depending on the time of year and the length of stay.