Puerto Rico offers the perfect balance of rum-soaked nightlife and tranquil retreat. The Spanish colonial buildings of San Juan set a perfect backdrop for a day of shopping and sightseeing. Hike the massive El Yunque rainforest to see waterfalls, stone towers, and colorful Puerto Rican wildlife. As far as beaches go, it doesn’t get better than the private sands of Isla de Vieques – particularly Mosquito Bay, where by moonlight the water glows blue-green thanks to magical microorganisms.

The glowing Mosquito Bay is a vision of bizarre beauty. Thanks to a bioluminescent microorganism, the water is a cool electric blue, looking somewhat like a fantastical sci-fi lagoon. Kayak or hop into a clear-bottomed pontoon boat to glide along the neon waters. Swimmers and snorkelers will adore the pristine, undeveloped beaches. Keep an eye out for the playful feral horses that gallop along the dunes, or visit the stately ceiba tree that’s been keeping watch over the highland for three centuries.

Conquering New York in one visit is impossible. Instead, hit the must-sees – the Empire State Building, the Statue of Liberty, Central Park, the Metropolitan Museum of Art – and then explore off the beaten path with visits to The Cloisters or one of the city’s libraries. Indulge in the bohemian shops of the West Village or the fine dining of the Upper West Side. The bustling marketplace inside of Grand Central Station gives you a literal taste of the best the city has to offer.

Walk the Freedom Trail the first time you visit Boston and you'll quickly get a sense of this coastal city's revolutionary spirit and history. But make sure you also explore some of Boston's fine museums (try the Isabella Stewart Gardner, featuring masterpieces displayed in their collector's mansion) and old neighborhoods (like the North End, Boston's Little Italy). You can't claim to have experienced real Boston culture, though, until you've watched a Red Sox game from the bleachers.

The windy city is a cornucopia of modern art, fine dining, cutting edge comedy, and die-hard sports fans. Snap a photo of your reflection in the silver Cloud Gate sculpture at Millennium Park before heading to Grant Park to get hit with the refreshing spray of Buckingham Fountain. There are dozens of museums and theater companies in Chicago, so a cultural experience is never hard to find. You’re sure to laugh your head off at the Second City Theater, the professional launch pad of many famous comedians.

Whether you’re a high roller or a low-key lounger, Las Vegas has something to suit your vacation taste. Sample fare from top chefs and cornucopian buffets, try your luck at one of the world’s premier casinos, or take in a spectacular show. Just wandering the Strip is enough to get your heart pumping. Once you’ve had enough of the razzle-dazzle, wave hello to the toothy sea life at the Mandalay Bay Shark Reef, hike Red Rock Canyon, or visit the Neon Museum, where old signs take on new life.

From Shoreditch’s swaggering style to Camden’s punky vibe and chic Portobello Road, London is many worlds in one. The city’s energy means that no two days are the same. Explore royal or historic sites, tick off landmarks from your bucket list, eat and drink in exclusive Michelin-starred restaurants, enjoy a pint in a traditional pub, or get lost down winding cobbled streets and see what you stumble across – when it comes to London, the possibilities are endless.

Barcelona feels a bit surreal – appropriate, since Salvador Dali spent time here and Spanish Catalan architect Antoni Gaudí designed several of the city’s buildings. Stepping into Gaudí’s Church of the Sacred Family is a bit like falling through the looking glass - a journey that you can continue with a visit to Park Güell. Sip sangria at a sidewalk café in Las Ramblas while watching flamboyant street performers, then create your own moveable feast by floating from tapas bar to tapas bar.

Lingering over pain au chocolat in a sidewalk café, relaxing after a day of strolling along the Seine and marveling at icons like the Eiffel Tower and the Arc de Triomphe… the perfect Paris experience combines leisure and liveliness with enough time to savor both an exquisite meal and exhibits at the Louvre. Awaken your spirit at Notre Dame, bargain hunt at the Marché aux Puces de Montreuil or for goodies at the Marché Biologique Raspail, then cap it all off with a risqué show at the Moulin Rouge.

This city, full of colorful homes, canals and bridges, is one of Europe's most picturesque capitals. Must-sees on any visitor's itinerary include the Anne Frank House, the Van Gogh Museum and the world's only floating flower market. Rent a bike and join thousands of locals navigating Amsterdam's labyrinthine streets, or just take in the sights on foot. For an unusual and memorable alternative to hotels, consider staying in a houseboat.

One of the world’s fashion capitals, Milan offers endless opportunities for chic shopping. Hit the artsy neighborhood of Brera for leather goods and Via Monte Napoleone for exclusive, expensive boutiques. The enchanting mosaics and glass vaults of Galleria Vittorio Emanuele II make shoppers feel like they’re wandering inside a painting. Take break from your spree to gape at the iconic Duomo, then grab tickets to a performance at La Scala. Post-opera, the Navigli district pulses with late-night activity.

Rome wasn't built in a day--and you'll need much more than a day to take in this timeless city. The city is a real-life collage of piazzas, open-air markets, and astonishing historic sites. Toss a coin into the Trevi Fountain, contemplate the Colosseum and the Pantheon, and sample a perfect espresso or gelato before spending an afternoon shopping at the Campo de’Fiori or Via Veneto. Enjoy some of the most memorable meals of your life here, too, from fresh pasta to succulent fried artichokes or a tender oxtail stew.