On the Kvarner Bay on the northern Adriatic Sea, the Croatian port city of Rijeka may be found. It is well known for being the entryway to Croatia’s islands. Buildings from the Habsburg era line Korzo, the principal promenade. The Croatian National Theater Ivan pl. Zajc, built in the 19th century, is located close by and features Gustav Klimt paintings on its ceiling. The Trsat Castle complex, which is perched on a hill and incorporates a religious shrine, provides sweeping views of the islands in Kvarner Bay.