Cardboard Playground Equipment "Nijiblock" Transforms Park Scenery

Overview

SaGAS Inc., a design firm based in Katsushika Ward, and Marusho Seikan Co., Ltd., a specialized cardboard manufacturer, have jointly developed the outdoor playground module "Nijiblock." It will be publicly unveiled on May 30 (Sat.) and 31 (Sun.), 2026, at the "National Greenery and Flowers Fair Katsushika" held at Hikifunegawa Waterside Park in Katsushika Ward, Tokyo.

This product, a fusion of the design prowess of internationally active architects and the material knowledge of artisans who have worked with cardboard for 80 years, leverages Katsushika Ward's proud local industries to propose "new ways to use parks" where multi-generational individuals, from children to the elderly, can actively engage.

Background: A New Experiment in Public Space Born from Katsushika Ward's Fair

The "National Greenery and Flowers Fair Katsushika," organized by Katsushika Ward, is an event that promotes the region's charm with a theme of greenery and flowers. Hikifunegawa Waterside Park (Kochi Kame Area), one of the venues for this event and located near Ohanachaya Station, is a waterside greenway cherished by residents. However, there was a need for "mechanisms within the park itself that attract people" to draw in a larger audience.

In response to this challenge, Jimo-ken Inc., which is supporting exhibitors at this venue, introduced SaGAS Inc. and Marusho Seikan Co., Ltd. The architect's desire to "create a park that embraces children's creativity" resonated with the local artisans' wish to "widely convey the potential of cardboard," leading to the planning of unprecedented cardboard playground equipment as a stage for advanced experimentation within Katsushika Ward's initiative.

Upon first seeing the completed prototype, the designer's child exclaimed, "It's a Rainbow Block!" Just as a rainbow appears fleetingly due to light refraction, the name "Nijiblock" was born from this single utterance, symbolizing people gathering and spreading out joyfully in the park. It was a moment when the project's philosophy was validated by a child's cheer.

Three Features of "Nijiblock"

Feature 1: Simple Yet Infinitely Combinable

With the design philosophy of "simple, but not simple when combined," a wide variety of configurations are possible by combining multiple Baumkuchen-shaped single units. Standing, laying down, stacking—each placement creates entirely different ways of playing and different scenery. The coloring includes 7 colors plus the natural cardboard color, intentionally retaining the cardboard aesthetic while expressing diversity.

By Gaku Sugiura, Co-Representative, SaGAS Inc.

Feature 2: Co-creation Process by 80-Year-Old Craftsmanship and Internationally Active Architects

Marusho Seikan, which has been working with cardboard for 80 years in Mizumoto, Katsushika Ward, and architects from SaGAS, who have won international design awards, engaged directly.

Through repeated prototyping while listening to the material's voice, a product that overcomes the constraints of outdoor use and low budget was born from the fusion of long-cultivated local techniques and the gaze of architects who design cities.

Marusho Seikan Co., Ltd.

Feature 3: The "Sense of Otherness" Appearing in Familiar Parks Connects Generations

The Baumkuchen-shaped cardboard playground equipment suddenly appears on the lawn of a well-maintained park. This "sense of foreignness (bug)" catches people's eyes and inspires unexpected ways of play from children, such as standing, laying down, or stacking. Starting from this sight, parents and grandparents naturally gather, creating a scene of lingering presence. "Nijiblock" transforms parks from "given spaces" to "places to actively enjoy," functioning as a mechanism to foster face-to-face relationships among those present.

"Nijiblock" Product Specifications (for this installation)

Shape

A 120-degree arc segment, dividing a circle with an outer diameter of 1,200mm and an inner diameter of 640mm into three parts.

Dimensions

Width 280mm × Height (Thickness) 280mm

Weight

Approximately 7kg (per unit)

Number of Units Manufactured

12 units

Material

Cardboard (partially painted: 7 colors + natural color)

Comments from Stakeholders

"I am delighted that we were able to create a space where children can experience with their whole bodies by leveraging the potential of cardboard as a material. The techniques our company has accumulated over 80 years have taken a new form on the stage of a park."

— Makoto Asano, Senior Managing Director, Marusho Seikan Co., Ltd.

"I hope that public spaces like parks can become places where visitors feel as if they are in their own homes. 'Nijiblock' was born from the desire to create opportunities for individuals to actively engage with public spaces, which belong to 'everyone,' by not predetermining its use or shape too much and leaving it to the imagination of the users. We expect that the sight of children playing freely will naturally attract parents and grandparents, fostering loose connections among people present. Through such scenes, we hope parks will become more familiar and beloved places."

— Gaku Sugiura, Co-Representative, SaGAS Inc.

"Bringing together Katsushika's local industries and emerging architects, and being able to experiment in a public space like the fair, feels like a new model for community development."

— Yoshino Ono, Representative, Jimo-ken Inc.