The Brijuni archipelago (Brioni in Italian) consists of two main pine-covered islands and 12 islets off the coast of Istria, just northwest of Pula across the 3km-wide Fažana Channel. Covered by meadows, parks, and oak and laurel forests (including rare plants such as wild cucumber and marine poppy) the islands were pronounced a national park in 1983.
The largest island, Veli Brijun, can be visited on boats booked through the National Park Office in Fažana; prices include a guided tour and entry to various sights. Mali Brijun can only be visited during the summertime Ulysses Theatre season, when performances are staged in an abandoned fort (the boats are included in the ticket price).
Note that most boat tours departing from Pula dock at the islet of Sveti Jerolim for a picnic lunch but then only cruise around the main islands, as they're not permitted to land.