The buzzing nightlife and narrow, winding streets filled with wine and tapas bars in Valencia's Old Town will be happily familiar to fans of Barcelona. But only Valencia has the 86-acre City of Arts and Sciences, which contains a science museum, a marine park, and L'Hemisfèric, a planetarium that resembles an enormous blinking eye.
The essentials: The Valencia Cathedral is home to an agate chalice rumored to be the Holy Grail; climb the bell tower's 207 steps for sweeping city views. In nearby Mercado Central, an Art Nouveau–style indoor market, you can find everything from Valencia oranges to jamón Serrano (like prosciutto, only Spanish).
Where to eat: Paella was invented in Valencia, and one of the city's most famous paella houses is century-old La Pepica on Malvarrosa Beach; a quieter alternative in Old Town is La Riuá, which serves 15 types of the saffron-infused rice dish.
Where to stay: At the Hotel Neptuno, next door to Valencia's yachting marina, amenities include plasma TVs, a roof deck, and a relaxed vibe at the beachfront terrace bar (double rooms from $223; hotelneptunovalencia.com).
Just as Prague emerged triumphant after the Velvet Revolution, the ancient walled town of Dubrovnik—nestled among the craggy cliffs and sunny beaches of the Dalmatian coast—has long recovered from the Balkan wars of the '90s.
The essentials: Walk the mile-long passageway around Dubrovnik's stone ramparts, overlooking a maze of terracotta roofs. Then enter the peaceful Old Town (which is closed to cars) and unwind at one of the open-air cafés on the main drag, the Stradun, where the architecture spans the Romanesque, Gothic, and Renaissance periods. Then hit the beach—choose from Banje's pebbled shores and Lapad's sandy stretches.
Where to eat: Try the swordfish carpaccio and grilled sea bass at the Atlas Club Nautika, where the people-watching is as good as the food. Croatia's proximity to Italy means pizza places galore; a favorite among locals is Mea Culpa (order the gorgonzola-and-bacon pie).
Where to stay: Hotel prices are high inside the Old Town's walls, but reasonable rates can be found just outside town at the Hotel Argosy, which has elegant interiors and a terrace overlooking the Adriatic (doubles from $236; valamar.com).
A historically rich, forward-thinking jewel of the Low Countries, Antwerp came into its own during the late '80s, when a cutting-edge group of fashion designers, the "Antwerp Six," began winning international renown.
The essentials: Nationalestraat is the premier shopping street; antiques-hunters should go to Kloosterstraat, then sample the butter truffles at nearby chocolatier G. Bastin. See Peter Paul Rubens's nudes at the Royal Museum of Fine Arts, or drop by Rubenshuis, the Baroque master's former home, now a museum.
Where to eat: Taste Belgian treats like steamed mussels and frites in Grote Markt; for Antwerp's most dramatic dining experience, head to contemporary French spot Het Pomphuis, a repurposed pumping station—think arched windows, soaring iron-accented ceilings, and exposed hydraulic equipment. The rib eye steak is sublime.
Where to stay: Family-owned Hotel Firean is housed in a 1929 Art Deco mansion with stained-glass Tiffany windows and breakfast in the camellia-filled garden (doubles from $258; hotelfirean.com).
Friendly locals, historic pubs, easy access to the countryside—imagine Belfast as a less crowded, less expensive Dublin. Since the end of Northern Ireland's "Troubles," its capital city has got a new lease on life that includes the opening of Victoria Square, an indoor-outdoor mall topped with a Fabergé-like glass dome.
The essentials: The Cathedral Quarter is popping with galleries and warehouse restaurants. Book a Black Taxi Tour to visit local landmarks, or journey to the coast to see the Giant's Causeway, an amazing volcanic rock formation consisting of 40,000 basalt columns stretching up to 40 feet tall (www.belfasttours.com).
Where to eat: Northern Ireland's star chef, Paul Rankin, emphasizes fresh seasonal ingredients at Roscoff Brasserie. If you want a nightcap, the Crown Liquor Saloon has mosaic-tiled floors, stained-glass windows, and "snugs," signature wooden booths with their own little doors.
Where to stay: Converted from a 19th-century seed warehouse, the Malmaison is a design-conscious hotel with a sleek bar and a "Homegrown & Local" restaurant menu (doubles from $295; malmaison.com).