A custom table surrounded by NET’s Museo chairs and poplar stools provides a space for the Sarmiento Tovo boys, Manuel, 5, and Julián, 3, to play with the toys their mother makes.

To access a secret play area in the 2 Bar House by Feldman Architecture, children clamber up climbing holds purchased from a local sporting goods store.

The compact living area is just off the kids’ room.

The children’s rooms, which are reserved for family and an extended network of friends, feature more custom Crasset-designed beds set against a vivid blue backdrop, courtesy of the French paint brand Zolpan.

The second bedroom, shared by two young children, offers a private space away from the rest of the home. The owners and architect alike made sure to maintain the apartment’s original features, including the ceiling moldings.

The kids make all the fun they need in their bedroom. Their bunk beds and shelving were bought at Ikea.

While she was pregnant and on maternity leave, Susanna tackled creative D.I.Y. projects to decorate Varpu's room, including stitching these festive cotton flag banners.

The Pinch (Department of Architecture at The University of Hong Kong: Yunnan, China) Few children experience the joy of running through a library, not to mention running on top of one, as they can do with this unique structure. Built in the wake of the 2012 earthquake that ravaged the province, the radical reading place offers seating, and as slide, on its curved timber roof.

A few children playing on the village basketball court.

From the exterior, the kaleidoscope is unassuming enough: a hexagonal window protruding from an simple rectangular building.

The kaleidoscope isn't the only whimsical part in the structure—take this polka-dotted room, for instance.

Mika, Kiku, and Kaz'ma play in the tatami room beneath the big skylight. The cushions on the floor were sent from Japan by the childrens's grandmother. The tatami mats were actually purchased in the UK from the Futon Company. Gaffney notes that they're not the proper dimensions of Japanese tatami mats, but they were much less expensive than importing the real thing.

This Murphy bunk bed, the Lollipop IN model from Resource Furniture, stows away flush to the wall when not in use.

Simon and Eva Luna play in front of a wall covered in Daks wallpaper from Walnut.

Jasper and Maeve take five. One of their requests was for their dad to create a secret door to connect their bedrooms together.

Even the children’s rooms, though peppered with colorful details, retain the stark white walls and minimal feel of the rest of the Egelunds’ home. The wooden bed is by Juno, the doll bed are by Flos Lampadina, and the shelves are Vipp.

Nate’s Bedroom Now three, Nate occupies coveted corner real estate in a third-floor room with a treetop-level view. “It’s a great space,” Casale says, “although it is the noisiest room in the house because of the street. But by now he’s so used to sleeping through all of the sounds, I don’t think it bothers him.” The brightness of the space is enhanced by an accent wall coated in fire engine–red chalkboard paint (Benjamin Moore Natura flat-finish paint in Vermillion mixed with unsanded grout) that Nate can scribble on—as soon as his parents get around to telling him that it’s allowed. A matching red pendant lamp from the Soho shop Kiosk hangs above a six-foot-tall teepee by Dexton Kids.

Cal and Macy jump rope with mom and dad.

Martin Buser sharing a quiet moment with his three comrades.

Measuing nearly 30 feet long and 6.5 feet tall, the kaleidoscope's mirrors reflect light from the outside as well visitors themselves. The architects say this "dream-like" space creates "a strange sensation of weightlessness."

Maja's room is filled with toys and includes a little desk area for drawing and writing.

Vandemoortele’s young sons and their friends enjoy the house’s nearly one-acre site as well, especially the lily pad–stocked pond.

Their parents’ seldom-needed stuff (luggage, winter clothes) is stashed in the higher cabinets. “Believe it or not, we have empty cabinets,” says Nikolova. “There’s space for everything.”

Sticker Shock Though colorful dashes here and there certainly enliven the sober interior, little adds a dose of whimsy like the wall decals found in the kids‘ rooms. The owl over Jonne‘s shoulder is available from Raumgerecht and the branch leaves are from the Dutch company Inke. raumgerecht.de, inke.nl

A sloping ceiling allows light into one of the children’s bedrooms. The bed is from CedarWorks.

The Gamby children have plenty of room to play; in addition to the pallet treehouse their dad built right outside of their bedroom window (with a slide to reach it!), they also have a playhouse in which to make believe.

The brass fittings are new to the project but are similar to metal that was originally used elsewhere in the project. The fittings, seen here in the children’s bathroom, will quickly acquire a dark patina.

While the debate rages on between the benefits of free play versus structured play, we can all agree that these play structures make any modern family home so much merrier. For a little perspective—in more ways than one—we turned to the Dwell team’s toddlers, Cedar Foss, Oliver Blue, and Madeleine McKinley-Hinson, who were all more than happy to pick a house, move in, and let the good times roll. See how the five playhouses fared in our product review. Photo by Peter Belanger.

Varpu's bed is piled with a motley assortment of plush cushions: “I love pillows and can’t resist when I see a nice one. Children love them too.” Don't miss a word of Dwell! Download our FREE app from iTunes, friend us on Facebook, or follow us on Twitter!

Fernando & Humberto Campana, Untitled (children’s chair), 2005 © Estudio Campana, Photo: Fernando Laszlo

The children’s bedroom features NET bunk beds and storage baskets from Mono, the design shop of Sticotti’s wife, Mercedes Hernáez.

The boys’ bunk beds are by Ikea.

The childrens' bathroom, which is just off the central hallway.