Kvarner is a large bay in the Adriatic Sea. Along with Istria, it is a part of the Northern Adriatic region. The area is known for its seamanship, oil industry and tourism. Rijeka, the largest Croatian harbor and refinery, is set there. Ship-building and metallurgy have a long tradition in the city and its surroundings, but are in decline now. The Kvarner islands are well-known tourist destinations. The Risnjak National Park is also worth visiting.