London comes alive when the sun comes out: Bright-striped deck chairs line parks, cafe tables cram pavements and people drape themselves on monuments to get a lunch-hour tan. But the city can also get hot … and sticky. Fortunately, London is home to more than a few outdoor swimming areas. Many of these "lidos," as Londoners call them, date back to the 1930s and are still in use. The fun doesn’t end there, either. Along with swimming pools, London has ponds, fountains and paddling pools. Check out our top picks for adults and kids alike to cool down in London -- and chill out.

Hyde Park 
This oasis in the heart of London is hugely popular with students, tourists, mothers and people on their lunch break. For a moderate fee, you can jump in and out of the 110-yard Serpentine Lido, sunbathe on the grass and watch your kids play in the sandpit, paddling pool and playground that adjoin the main pool. Another place for dipping your feet is the Princess Diana Memorial Fountain. Designed by American-born landscape architect Kathryn Gustafson, this isn’t a traditional fountain -- more like a large, oval ring of stone in which water runs in unpredictable directions over granite features. In the summer, the grassy area around the fountain is lined with sunbathers or toddlers and children splashing about, although it’s best not to walk or run in it.

Brockwell Lido 
Popular during the week with freelance media types and trendy mothers, this Olympic-size 1,640-foot outdoor pool in south London is fondly known as Brixton Beach. It has a laid-back vibe and the pool is large enough for a game of handball without disturbing the serious swimmers doing lengths. It was first opened in 1937, and the changing rooms are in an Art Deco building. But there’s nothing old about the facilities: Inside you'll find a hydrotherapy pool, a gym, sauna, steam room and exercise studio offering a range of classes (try the yoga to feel really chilled out). Outside the complex is an expanse of parkland that you can picnic in when you tire of the water.

Hampstead Heath 
This large green expanse in north London contains 3 natural ponds that are suitable for swimming -- one for men, one for women and one coed. All are deep, natural freshwater ponds surrounded by trees without a shallow end, so children under 8 are not allowed. You can hang onto strategically placed rubber rings in each pond when you want a break, but you can only get in and out at one end -- so you should be a confident swimmer. For a more traditional swimming experience, head to the 197-foot Parliament Hill Lido at the Gospel Oak entrance of the park, where you can do laps and children can paddle in the shallow end.

Coram Fields 
This 5-acre playground is a good place to know about if you’re coming to London with children in the summer. Located in the central London area of Bloomsbury, it is a child-only zone ( adults can only access the grounds if accompanied by a child!). The playground is a great reward if your kids have obediently trailed around the nearby British Museum, looking at the objects that detail 2 million years of history. After all that learning, they'll welcome the chance to run around the large grassy area, slide down the slides, scramble up the climbing frames, build castles in the sandpit and splash about in the paddling pool. And when they are thoroughly worn out, they can visit Coram’s Fields’ city farm, where they can pet the resident goats, sheep, guinea pigs and rabbits.

And Don’t Miss … 
You’ll also find splashes of cool water in unlikely places around London. Trafalgar Square boasts 2 huge fountains. Plus, there are dozens of elegant water jets in the courtyard of Somerset House (home to the small art museum, The Courtauld Gallery). Appearing Walls, outside of the Royal Festival Hall on the South Bank, is an interactive water installation designed by Danish artist Jeppe Hein, where changing water jets surround you in a wall of water. No matter how hot London gets, these attractions will offer welcome refreshment.