Taking the kids out can get expensive. Fortunately, London has plenty of places where children can play and learn for free. The following list gives a mix of outdoor and indoor options. Please suggest additions in the comments, and we will add the best ones into the mix.

All venues are suitable for infants through to teenagers, unless otherwise noted at the end of the entry.

Parks and outdoor fun

A secret park for kids: Coram's Fields (Central)

'No adults unless accompanied by a child,' says the sign on the gate to Coram's Fields. This seven-acre park in the middle of Bloomsbury is off-limits to most passers-by, but turn up with a child and you can enter for free. Inside, you'll find play equipment for all ages, with a cafe, drop-in activities and even a small city farm. It's open 9am-dusk every day. Nearest station: Russell Square (Piccadilly line). Website. Londonist feature.

Dance in the fountains: Granary Square (Central)

London has a fine collection of play fountains, including the epic sprayers in the Olympic Park and the seasonal fountains at the Southbank centre. Perhaps the best are the dancing fountains in King's Cross, which decorate the piazza in front of St Martin's College. The water bubbles and spurts to different rhythms and heights, with coloured lighting at night. You can even take control at certain times with the Granary Squirt phone app. Nearest station: King's Cross St Pancras. Website.

Meet the Pelicans: St James's Park (Central)

The Royal Park has kept a group of the ungainly birds since 1664, when the Russian Ambassador offered a pair to Charles II. The unusual gift has kept generations of Londoners and visitors entertained. See them being fed everyday between 2.30pm and 3pm, at the eastern end of the park's lake. Nearest station: St James's Park or Charing Cross. Website. Londonist feature.

A quiet clamber near the South Bank: Nelson Square (Central)

London's South Bank and Bankside areas have just about every form of entertainment going — except for children's play areas. Yes, there are some token climbing things near the London Eye, but they're always crowded. For an altogether more secluded play, head to this quiet residential square off Blackfriars Road. It's no more than 10 minutes walk from the river, even with little ones in tow. The play equipment is a bit more adventurous than most, with giant tarpaulin slides, crazy rope nets and trampolines, as modelled by Londonist Junior in our photo. We had it all to ourselves for ages. Nearest station: Southwark (tube).

Pond Dipping: Camley Street Natural Park (Central)

The former railway lands north of King's Cross have changed beyond all recognition over the past decade. One tenacious mainstay, opened in 1985 by Ken Livingstone, is this cute little park over to the north-west. It's the perfect place to spot frogs, insects, butterflies and even kingfishers. London Wildlife Trust runs regular family activities, including pond dipping, bug hunts and wildlife arts and crafts. Nearest station: King's Cross St Pancras. Website.

Goats on a train (almost): Kentish Town City Farm (North)

If you've ever passed through Kentish Town on the mainline or Overground, you might have spotted an unexpected goat or two. Kentish Town City Farm inhabits an awkwardly shaped stretch of land between these two rail routes, and even extends onto a bridge over the Thameslink. The farm puts on several free creative classes, although the play scheme and some classes have a small fee (entrance to the farm itself is always free). Nearest station: Gospel Oak (Overground) or Kentish Town (tube, Thameslink). Website. Londonist feature.

Exotic animals: Golders Hill Park (North)

Long a Londonist favourite, this beautiful park abuts on to some of the most impressive features of Hampstead Heath, such as the Pergola and Hill Garden. The kids will be more interested in the small 'zoo', which includes such exotics as wallabies, coatis and kookaburras. There's even a pair of dinosaurs — a rusty sculpture last seen in the Square Mile, by the Chapman brothers. Nearest station: Golders Green. Website.

Paddle at Brockwell Park's water park (South)

Brockwell Park is easily the best park in London. No argument. Where else combines a stylish lido, free BMX track, impossibly good cafe, sports pitches, walled garden, amazing views AND a miniature railway, all in one place? Nowhere. You can add to that a top-notch children's play area, with plenty of splashy fun. It's a full day-out. Nearest station: Herne Hill (Thameslink). Website.

Meet the Dinosaurs: Crystal Palace Park (South)

Little-known fact: of the 29 animal models on show in Crystal Palace Park, only four represent dinosaurs. Even so, the Victorian sculptures are universally known as such, and have fascinated youngsters for generations. While you're there, look out for the cool sandpit where you can 'dig' for buried dinosaur remains and eggs. Nearest station: Crystal Palace (Overground).

Incredible slides: Victoria Park (East)

This grand old park has more sides to it than a Dungeons & Dragons dice. While adults admire the gardens, lakes and perimeter pubs, the kids can get stuck into one of the best playgrounds around. No mere swings and see-saws here. Clamber over boulders and spider nets, splash about in pools, and ride two of the longest open-topped slides in London. Nearest station: Hackney Wick (Overground). Website.

Meet Alpacas: Mudchute Farm (East)

London has plenty of urban farms, but Mudchute offers three distinct advantages over most. (1) It's free. (2) You can take quirky photos of the Canary Wharf skyscrapers with sheep in the foreground. (3) It has llamas and alpacas. The spitty camelids are joined by the usual mix of pigs, goats, chickens and other farmyard staples in a spacious location with a decent cafe. Nearest station: Mudchute (DLR). Website.

Diana Memorial Playground (West)

Not to be confused with the Diana Memorial Fountain, in neighbouring Hyde Park (though that's also free, and worth a look), this sandy play area in Kensington Gardens reckons to get a million visitors a year. It's easy to see why. The centrepiece pirate ship looks like the kind of thing you expect at paid attractions, but there's much else to explore on the periphery. The nearby Elfin Oak is enchanting whatever your age. Nearest station: Queensway. Website.

The hills of Northala (West)

This remarkable set of artificial hills is built from the rubble of old Wembley Stadium. Kids will burn off excess energy racing directly to the top, while mummy and daddy take the slow, spiral route round the edge. When you're done with the hills, Northala Fields includes a couple of cracking playgrounds — the one pictured for older children, and a nifty little area for the under fives elsewhere. Could do with a better cafe, though. Nearest station: Northolt (tube), free parking also available. Londonist feature.

A beach in the woods: Ruislip Lido (West)

Ruislip might seem a little far out of centre for some, but it's worth the trip. An idyllic lake surrounded by woodland trails would be reason enough, but this picturesque spot also includes a decent-sized beach. When you're done building sand castles, there's 60 acres of woods to explore, plus a Woodland Centre with displays about the history of the area. All of this is free, but those who choose to open their wallet can also enjoy a cafe, pub, tearoom, and one of the south-east's best miniature railways. Nearest station: Northwood Hills (Metropolitan line), or free parking. Website. Londonist video.

Museums and galleries

Take a trip on a magic carpet: National Gallery (Central)

We're so lucky in London to have so many free museums and galleries. Many also put on free activities for children. One of the best regular slots is the magic carpet storytelling at the National Gallery. Said carpet 'lands' in front of a different painting each time, which serves as the inspiration for storytelling. You need to prebook on the day, so turn up early to grab a space. Nearest station: Charing Cross or Leicester Square (tube). Website. Suggested age 2-5.

Handle the oldest object in London (South)

This jagged object is known as the Gibeon meteorite. It's made of iron and nickel and was forged some 4.5 billion years ago, during the formation of the solar system. You'll find it on display inside the South Building at the Royal Observatory, Greenwich. Although much of the observatory (and planetarium) are paid attractions, there's still plenty to see in the free section. After stroking the meteorite, kids can learn more about astronomy, see a replica of the Beagle 2 Mars probe, and get inspired by the Astronomy Photographer of the Year exhibition (Sept-July each year). Nearest station: Cutty Sark (DLR) or Greenwich (mainline). Website.

Meet the walrus: Horniman Museum (SOUTH)

Teach your kids about animals, anthropology and musical instruments at one of the capital's most eclectic museums. The Horniman's best-loved treasure is the giant, over-stuffed walrus who presides over the natural history collection. The 16 acre gardens contain a nature trail and sundial trail, and command impressive views across London. Nearest station: Forest Hill (Overground). Website.

Shovel coal and sell fish: Maritime Museum AHOY! gallery (South)

All children love pirates, for some reason. Bend their nautical yearnings away from such criminal pursuits, with a trip to the National Maritime Museum's AHOY! gallery. This free space includes plenty of briney fun, from helping to stack a container ship, to stoking an engine, to pretend fishmongery. Honestly, it really is fun. Nearest station: Cutty Sark (DLR). Website. Suggested age 0-7.

Relive your own youth: Museum of Childhood (East)

This Bethnal Green museum works for all ages. Displays show toys and games from every decade. You can impress the offspring with the incredibly low-tech stuff that was considered a toy in your own childhood. Needless to say, the museum also puts on plenty of free activities and play sessions for different age groups. Pick up a free family pack from the information desk. Nearest station: Bethnal Green (tube). Website.

Explore Sailortown: Museum of London Docklands (East)

While the central Museum of London has a well-known recreation of a Victorian street, its Isle of Dogs sister site is all about the docks. Sailortown is a splendid recreation of the ramshackle buildings that once characterised Wapping and Shadwell. Kids will love exploring this twilight world of cobbled arches and dimly lit mock-shops. Meanwhile, the Mudlarks gallery offers soft play for the nippers, and nautically themed hands-on displays for the older children. Nearest station: West India Quay (DLR). Website. Suggested age: up to 8 for Mudlarks

Splash about at the Science Museum (West)

The Garden, located in the museum's basement, is really a hands-on interactive play area for younger children. The four areas — construction, light, water, sound — are all fun, but the water-play section is particularly engaging. Look out for the bench that farts when you sit on it. Nearest station: South Kensington (tube). Website. Suggested age 3-6.

Other fun stuff

Platform 9 ¾: King's Cross (Central)

So your kids want to catch the Hogwarts Express? They can't. It doesn't exist. But the next-best thing can be found inside the concourse of King's Cross mainline station (read our full expose). Potter fans of all ages queue up to pose with a luggage trolley, on the supposed threshold of Platform 9 3/4. The magical platform has moved around a few times over the years, but has now settled into a compromise position between Platforms 8 and 9. Nearest station: King's Cross St Pancras (obviously). Website.

Watch Tower Bridge open (Central)

Ah, the simple pleasure of watching a bridge open. But don't discount the experience as too touristy. Tower Bridge, with its bascules standing proud, is an unforgettable sight for anyone. The best views are perhaps from the More London area on the south bank, around City Hall — but you can get a good eyeful from either side of the bridge. It raises more often than people think — typically three or four times a day. Nearest station: Tower Hill (tube) or Tower Gateway (DLR). Website with scheduled opening times.

Into the clouds: Sky Garden (Central)

The Walkie Talkie building (20 Fenchurch Street) was once able to melt cars, until its powers were taken away. You can tell the kids it was a bit like the plot of Superman 2 — if kids still watch those ancient movies. The 'death ray', caused by a concave wall focussing the sun's rays, is long gone, which is a pity as it could have served as an educational visitor attraction in its own right. Instead, families can still book a trip up to the Sky Garden, London's highest free viewing platform. Nearest station: Monument (tube). Website.

Got further suggestions? Add them to the comments below. The best will be added to the article.