Situated under the U-ka mountain and overlooking the beautiful blue Adriatic Sea and the islands of Krk and Cres, Opatija is a popular destination for tourists from all over the world. A pleasant climate throughout the year and the natural beauty that surrounds it forces the tourists to come back to her again. Opatija was a well-known spa resort in the 19th century, which means that after you're finished with exploring the city you can devote some time to your health.