Climbable tubes made of wrought-iron netting wrap around two aircraft fuselages, a fire engine, a castle turret, three tram cars and a seven metre tall cupola in this adjunct to the St. Louis City Museum. Iron “slinkies” narrow and spill out onto a three-storey slide. Designed by Bob Cassilly.

To create an undulating climbing space that meanders through the trees, designers erected two green steel pipes with a net strung between. In some sections, traversing the structure can involve swinging from ropes with rotating plates.

A Möbius strip-like climbing wall made of a textured anodised aluminum sheet, studded with polyester resin (fake rock) handholds, forms a challenging landscape to explore. Therapists use the climbers to help children overcome sensory-processing disorders.

What happens to a jungle gym when it’s compressed? It turns into a maze, a fortress, a rock-climbing wall or a soccer goal. Sixty children can comfortably fit in and on Wall-holla, a structure 5 metres tall and 15 metres long.

Wall-Holla's exceptionally efficient design compresses a colourful 3D climbing ribbon between two mesh walls, creating a unique experiential environment that, due to its compact size, can fit into even the most limited playground site.

In this travelling geometry exhibit and playspace, children roam through walls of torqued cubes, parabolic curves and wavy mirrors; play with stacked forms and glowing building blocks; and climb gyroids and a stellated rhombic dodecahedron. They might even learn some math as they do.

In 2010, the Exploratorium science museum in San Francisco debuted its travelling playground, an innovative concept with an innovative goal: to introduce children to the complexities of geometric shapes by letting them physically explore them.

NEOS introduces videogame elements - blinking lights, buttons, beepers and timers - into outdoor playgrounds. Players run, jump, and work together to chase down light as it bounces from panel to panel throughout the rubberised metal structure. The light-tag games are aerobically intense and last just a minute at most.

Nine objects - mounds, bumps, walls, waves, noodles - form a playground-in-a-box. Children can spin the bumps, fit the waves together to form a slide, and use the walls (which are semicircular) to build tunnels or, flipped, as seesaws.

The London-based brother and sister team behind Snug & Outdoor describe themselves as a “team of artists” who aim to augment schoolyards and public land by reclaiming underused spaces.

A crashed plane, the belly of a whale and topsy-turvy houses conjure entire worlds. In these wood and metal spaces, playing becomes a form of storytelling: mounting rescue missions, balancing on wings, and trying not to fall into the sea (or sandbox, as it may be).