Runyon Canyon Park
It seems like tabloids feature photos of celebs running, hiking or walking their dogs in Runyon Canyon Park every week. At 160 acres, this park offers hiking trails of various difficulties, so it's no surprise that stars of every age and fitness level are spotted here (and the no-leash policy means it's also a popular spot for bringing pooches on a stroll). Josh Duhamel and his wife, Fergie, are often spotted jogging together, and when Scarlett Johansson was getting hot and heavy with Sean Penn (remember those five minutes?), she and her then-boyfriend got hot and sweaty on a jog with pal Owen Wilson.
Where to Stay: The Hollywood Roosevelt Hotel is just a 10-minute walk from one of the park's entrances. The hotel combines the shimmer of silver-screen history with a cutting-edge party scene centered around the massive pool.
Although New York City does not have the sprawling open spaces that some areas of L.A. offer, Central Park is the crown jewel of the bustling metropolis. At 843 acres, it's a popular spot for working out (and there are tons of ways to break a sweat), though the running track around the Reservoir --- about a 1.5 mile loop -- may be the most frequented fitness destination. Celebs recently seen sweating there include Chris Noth, Heidi Klum, Gywneth Paltrow and Mark Ruffalo. Not a runner? Visitors can also bike, kayak, ice-skate (during the winter), and even rock climb. Central Park is also a popular spot for movie sets, too, so keep your eyes peeled.
Where to Stay: Located across Columbus Circle from Central Park, the Mandarin Oriental offers a dizzying array of modern luxuries -- a 75-foot pool, one of the city's best spas, sweeping views from nearly every common area (and some rooms have Central Park views), and superb on-site fine-dining options.
While some star-gazers may set up a towel and relax in the sun, you'll have more luck getting up close and personal with stars at Malibu Beach if you hit the waves. David Beckham and Gerard Butler enjoy riding the surf and Matthew McConaughey has been seen paddle-boarding in calmer waters. McConaughey has also been a participant in the celeb-heavy Nautica Malibu Triathalon, along with funnyman Will Ferrell. Tiffani Thiessen (of Saved by the Bell fame), The Hangover's Ed Helms, John Cryer, and Bachelor host Chris Harrison all showed up for the race's 25th year, which raised money for cancer research.
Where to Stay: A 30-minute drive from Malibu, Hotel Oceana Santa Monica more than compensates for its lack of on-site features --no spa, a long walk to the beach-- with great design in its large rooms, a welcoming atmosphere cultivated by personal service and a relaxed, low-key vibe.
The trend du jour, Soul Cycle is an upbeat spin class that combines top-notch, top-40 remixes with hardcore instructors who won't let you get by with anything less than working your butt off. Classes are pricey (we're talking really pricey), but they come with an above-average chance of spotting someone famous. Kelly Ripa is a huge fan (she even convinced pal Anderson Cooper to join her and now he's hooked) and Brooke Shields, Katie Holmes, and Jake Gyllenhaal are also avid spinners.
Where to Stay: Just a few blocks from one of the city's Soul Cycle studios, W New York -- Union Square greatly resembles other Ws in New York: Comfortable beds, modern rooms, an excellent gym, and plenty of business travelers in the butterfly-decorated, techno-soundtracked lobby.
High Line Park
Built on a former elevated railroad track, the High Line Park was instantly popular after its opening in 2009 -- and now that the park expanded, it's a nice spot for jogging (plus, if you need a rest, you can relax on one of the lounge chairs that slide along the tracks). As you walk, jog, or run along, you can enjoy views of the river and you may even spot a celeb; in summer 2011, Beyonce showed off her baby bump at the park and Orlando Bloom and Miranda Kerr brought son Flynn on a walk there recently. It's no surprise that the High Line is a celeb hotspot, as many celebs -- including Kevin Bacon, Edward Norton, Amanda Peet, Glenn Close, Hilary Clinton, and Martha Stewart -- made significant donations towards the renewal project.
Where to Stay: The Standard New York hovers above the High Line on concrete pillars. This one-of-a-kind Meatpacking District hotel offers 337 light-flooded, ultra-mod rooms with panoramic views of the city; one restaurant, several popular bars and excellent service. It might just be the hippest hotel in New York City.