The highlight of Southern Dalmatia is undoubtedly the majestic walled city of Dubrovnik, from 1358 to 1808 a rich and powerful independent republic, which exerted its economic and cultural influence over almost the entire region. Jutting out to sea and backed by rugged mountains, it's an unforgettable sight and now Croatia's most upmarket and glamorous destination.
From Dubrovnik a ferry runs all the way up the coast to Rijeka in the Kvarner region, making several stops along the way, and occasionally extending its itinerary to include an overnight lap from Dubrovnik to Bari, Italy. There are also regular local ferry and catamaran services from Dubrovnik to outlying islands. The nearest and most accessible of these are the tiny car-free Elafitis, ideal as a day trip for someone on a short stay who still wants a brief taste of island life.
Moving down the mainland coast, Cavtat was founded by the ancient Greeks. Today a sleepy fishing town through winter, it turns into a cheerful holiday resort come summer, with a palm-lined seaside promenade, several sights of cultural note, and a handful of reasonably priced hotels.
Back up the coast, northwest of Dubrovnik, lies the village of Trsteno, with its delightful Renaissance arboretum stepping down toward the sea in a series of terraces. Proceeding northwest one arrives at Ston, known for its oysters and mussels, and its 14th-century walls forming the gateway to Peljesac Peninsula. Peljesac is of particular note for its excellent red wines: several families open their vineyards and cellars to the public for wine tastings. The main destination here is Orebic, a low-key resort with a good beach and water-sports facilities, backed by a majestic hillside monastery. From Orebic there are regular ferry crossings to Korcula Town, on the island of Korcula, one of the most sophisticated settlements on the Croatian islands, with its fine Gothic and Renaissance stone buildings bearing witness to almost 800 years of Venetian rule. Nearby Lumbarda provides a good stretch of sand beach, plus a delicate white wine known as Grk. In contrast to Korcula, the sparsely populated island of Mljet offers little in the way of architectural beauty but has preserved its indigenous coniferous forests, which rim the shores of two emerald-green saltwater lakes. They are contained within the borders of Mljet National Park, a haven for hiking, mountain biking, swimming, and kayaking. If you're travelling from Central to Southern Dalmatia by road, you'll pass through a narrow coastal strip given over to Bosnia-Herzegovina, so have your passport at hand for the border checkpoint. Most Croatian buses have a 20-minute stop here so people can jump off and shop, since many things—notably cigarettes—are much cheaper in Bosnia.