Karlovac is located at the junction of 4 rivers; the Kupa, Korana, Mrežnica and Dobra, and is therefore locally known as "the city on four rivers". In fact, only three rivers flow through the city itself and the fourth, the river Dobra, is a bit on the outskirts. Because Karlovac is the home of one of Croatia's most famous breweries, natives also sometimes joke about the "fifth river" – the one made of beer.
The town plan is unique in Croatia, as the historic town center is in the shape of a 6-pointed star, this being a design feature of the fortifications that surrounded the city. In fact,the town itself and surrounding fortifications were founded in the 16th century for the purpose of strengthening the area's defenses against the invading Ottoman Empire, and the star-shaped plan was a feature in many fortifications of the day, which made it impossible for attackers to attack a wall on one star point without being shot at from behind by defenders on another wall on an adjacent star point. After the Ottoman threat faded, the city walls were torn down and the moats surrounding them were emptied. Today only one small section of the original walls remains, while the former moats are now large parks and recreational areas.
While Karlovac isn't really a popular tourist destination in Croatia, being on the way from Zagreb to the coast makes it a convenient and nice place to spend a half day or full day trip, and who knows, perhaps more?
Old Town Dubovac: a fort from the 15th century. Situated on one of the nearest hills, it boasts a beautiful natural setting and great views of the city. In summer some organized events take place, such as concerts in the fort and a medieval festival. It takes about 30 minutes to get here on foot from the city center, which can prove to be an enjoyable walk through tree-lined Marmontova avenue, and then a short climb on the forested slopes of the hill the fort is built on.
Parks and promenades: the town is packed full of parks and green areas, and the entire area surrounding the historical part of the city, as well as wide trenches that were once water-filled moats, are now one large uninterrupted park. There is a modest botanical garden surrounding the forestry school, and a picturesque, densely forested old park on the river Korana surrounding the Srakovčić hotel, which is known as Vrbanić public garden. A large grass field called Vunsko polje (polje = field) is also near the Korana and has various free sports courts.
City museum: Houses artifacts from the city's history and is located in the old historic center, a minute on foot from the large Holy Trinity church, in what is supposedly the oldest house in the city.
Historic part of the city: Locally known as the "Star" (Zvijezda in Croatian), this is the area that was originally within the city walls. Sadly it has seen better days, with many houses and buildings now vacant and decaying (though this may hold a certain charm to it for some people) and the area in general feeling depressingly empty. The main street that goes through the Star is called Radićeva street and has several shops, bookstores and cafes. It livens up the most at the beginning and end of school shifts, when masses of pupils from five high schools are walking through. Most of the Star is a dedicated pedestrian zone.
Rivers & Beaches: Korana, Mrežnica, Kupa, Dobra. In summer the river banks turn into populated beaches and are great for whole day activities. There is an official beach on the Korana river called Foginovo, with cafes, sports facilities, jumping platforms and a lifeguard service. The river Kupa is polluted and unsuitable for swimming within and downstream of town, but a bit upstream from town may be clean enough.
Mountain Biking. There are lots of preserved trails all around the city, especially in the large Kozjača forest that begins on the city's western edge (Old Town Dubovac is right on the edge of Kozjača) edit
Rafting and Kayaking. Available in the summer months on the rivers Korana, Mrežnica and Dobra, with the more upstream parts of these rivers a bit away from the city being particularly beautiful.edit
Karlovački Dani Piva, . End of August. Annual beer festival. The most crowded place at that time of summer, with various folks around. You can grab a beer and pretzel and see if there's music which suits you at one of several stages.edit
Karlovac Piano Festival, (firstname.lastname@example.org), . July. Karlovac Piano Festival features music lessons and master classes with world renowned piano teachers, recitals, as well as International Piano Competition. edit
International folklore festival. Early July. Featuring authentic music and dances from various cultures from all around the world, this annual, free of charge, open air venue takes place on the basketball court in the city park, basically in the city center.edit
There are not many shopping options. Modest shopping "malls" are Supernova (near the motorway toll station and Hotel Europa) and Karlovčanka (city center). Locals usually do more serious shopping in Zagreb.
Karlovac is home to one of Croatia's two most popular breweries, and its Karlovačko beer which is a must try.
The main street is called Korzo, and together with Promenada (the adjacent part of the park) and other nearby streets is home to many cafes and bars where you can enjoy sipping a coffee in the day or party on weekend nights.
Almost every year one or more people drown swimming in Karlovac's rivers. Be very careful around numerous waterfalls and rapids which are often popular swimming spots.
Although minefields left over from the war have been cleared from the immediate vicinity of the city, if hiking off the beaten path in remote areas east or south of the city, pay attention to any minefield warning signs and do not proceed if you see any. As these signs are sometimes stolen, it's good to inquire about mine danger in suspect areas.