Sat on what look like furniture dolleys, the boulders were placed on Southbank Boulevard in Melbourne to create an open environment for children to climb and explore intuitively.
"[The boulders are] delicately resting, as if recently rolled into position and the light-weight brake mechanism engaged," Hewson told Dezeen.
"Simple traditional play equipment appears loosely lashed to the boulders, perhaps as if a cheeky community group assembled it over the weekend," he explained. "Leftover pieces of construction waste rest in the recesses of the stone, at times acting as useful hand holds for the adventurous child to hang off."
There are no handrails or platforms in the playground. Slides, swings, monkey bars, ropes, and a linear sandpit connect the spaces in and around the boulders.
A series of small objects – including miniature animals, toy cars, garden hose and other domestic items – were hidden throughout the project to "reward exploration".
The floor surface around the boulders appears to be bluestone pavers, similar to those you will find across Melbourne. They are in fact soft-fall matting, made to look like a regular Melbourne sidewalk.
The boulders were sourced from the same Victorian quarry that provides the bluestone pavers for Melbourne's streets.
A series of "runaway baby rocks" were distributed throughout the wider Southbank Boulevard area as an invitation to the playground.
Sited on what was previously a roadway, the $2.4 million project takes its name from a 1962 Diane Arbus photo Rocks on Wheels which depicts fake rocks being rolled into place on furniture dolleys at Disneyland, California.
The "weightless absurdity" of the fake rocks in Arbus' photo has been reproduced at Southbank, only the rocks at Southbank are real and the reinforced trolleys beneath have been integrally and carefully designed to support them.
There was initially some concern in Australian media when the playground opened in November 2022 that it was risky or unfinished but Jocelyn Chiew, director of the City Design Studio at the City of Melbourne, told Dezeen "it was designed with safety as a core priority".
"The design and build were rigorously tested by the project team and signed off by playspace auditor, DMC Design," she explained.
"The concepts and benefits of 'free play', 'nature play' and 'risk play' in public space are well documented however they have rarely been so comprehensively embedded and expressed in public space as they are at Rocks on Wheels in Southbank."
The project is part of a $44 million council upgrade to create public space in the densely-populated Melbourne suburb of Southbank.
City of Melbourne Council provided site design, landscape architecture, industrial design, project management and horticultural services.
Mike Hewson has completed five large-scale public art commissions in Australia, many of them are sculpture-park-come-playgrounds. His aim is to pioneer new ways to merge conceptual art projects into the public realm.
Other recent designs for playground and playscapes include an architectural playground in Doha that features miniature versions of four well-known buildings in the city and series of five pink marble play sculptures in Billund, Denmark.
The photography is by Mike Hewson.