Sweating for world peace at the Expo saunas

While hot-spring bathing is still Japan’s go-to form of wet and sweaty relaxation, Nordic sauna culture has been making massive inroads across the country in recent years. The steam-room boom has even reached Expo 2025 Osaka, Kansai, where the toughest reservation of them all is neither any of the national pavilions, nor one of the stunning ‘signature pavilions’ produced by some of the country’s brightest scientific minds – it’s a sauna.

Named ‘Taiyo Tsubomi’ – roughly ‘buds of the sun’ – the Expo sauna is a unique take on the Finnish sweat chamber, composed of petal-like air membrane cushions that converge to form a sprout reaching toward the light. Tickets for the 14-person bathing sessions that take place daily are doled out through a devilishly competitive lottery system, and scoring one is considered a minor coup among sauna heads.

But whose idea was it to build a high-tech sauna at the Expo, and how does this decidedly laid-back project fit with the World’s Fair’s message of building a better society for the future? We asked Yuki Nohmura, president of the company behind Taiyo Tsubomi, and got an exclusive look at the in-demand attraction – along with a story of how the cutting-edge materials Nohmura’s firm specialises in make some of the Expo’s most spectacular sights possible.

Steamy rituals, naked connections

A cluster of pearly white, translucent structures standing tall on the edge of Osaka Bay, the Taiyo Tsubomi saunas are hidden away in a secluded corner of the Expo’s Green World area. Constructed by the Taiyo Kogyo company using ETFE film, a lightweight, durable and energy-efficient resin material, the saunas harmoniously blend natural elements with advanced technology.

Bathing in them isn’t your average sweat-cool-repeat deal. What goes on inside is best described as a series of rites – 11 consecutive ‘actions’ that all participants undergo. ‘If regular sauna bathing is like ordering à la carte,’ says Taiyo Kogyo’s Yuki Nohmura, ‘our sauna is a multicourse meal.’

The idea is to stimulate the senses and encourage connection. ‘At the end, all 14 bathers reach a state of reconnection – to themselves, to their fellow participants, to Earth,’ explains Nohmura. ‘Sauna bathing heightens the senses. Relaxed, you notice things you hadn’t paid attention to before – birdsong, the wind, how blue the sky is.’

There’s a strong spiritual aspect to the Expo sauna experience, with the story of the Japanese sun deity Amaterasu providing the foundation for the 11-part ‘ritual’. The core message Nohmura hopes to send with his saunas, however, is more universal.

‘I think sauna bathing has the power to further peace,’ he says with a smile. ‘At the Expo, you get visitors from all over the world – Americans and Russians, Israelis and Palestinians, Indians and Pakistanis. Our sauna offers everyone a place to reconnect, to build ties – and these ties can help bring about peace in the future.’

Festival focus

While the sauna experiment marks a new avenue for Taiyo Kogyo, the Osaka-based materials company is no stranger when it comes to Expos. On the contrary, Nohmura’s firm has been a key player at World’s Fairs ever since the first Osaka Expo in 1970, when it helped build and run several pavilions on the sprawling grounds of what is now Expo ’70 Commemorative Park.

And the company’s involvement with global mega-events doesn’t stop there: Taiyo Kogyo has long been a fixture in stadium construction for sporting extravaganzas including the World Cup, and is currently part of the team rebuilding the NRG Stadium in Houston, Texas to prepare it for hosting matches during the worldwide football showcase’s 2026 edition.

For Nohmura, these events all have something attractive in common. ‘They’re all festivals, and at Taiyo Kogyo there’s nothing we love more than a good festival,’ he says. ‘Festivals have the power to bring people together, to excite and to move them.’

And some festive fun might be just what Japan – and the world – needs right now. ‘An event like the Expo can provide a boost to culture, technology, even society as a whole,’ Nohmura argues. ‘And since it’s one of the world’s biggest festivals, you get that cosmopolitan atmosphere. It’s an opportunity for people from all over the globe to get to know each other, make friends – and strive for a better future.’

Material worlds

Nohmura’s passion for the Expo is reflected in the extent to which his company is engaged with the ongoing 2025 edition. Besides the Taiyo Tsubomi saunas, Taiyo Kogyo is a major driving force behind structures such as null², the ‘signature pavilion’ by media artist Yoichi Ochiai.

The mirrored exterior of null² vibrates and warps, distorting the viewer’s senses. Its striking appearance is made possible by a new sheet-like material developed by Taiyo Kogyo and fitted onto the pavilion by the company’s architects and engineers.

However, the reflective surfaces of Ochiai’s pavilion weren’t even the toughest task for the Taiyo Kogyo crew at Expo 2025. ‘What we really struggled with was Nishijin-ori,’ says Nohmura. This traditional brocade from Kyoto, which covers the clam-like pavilion shared by housing manufacturer Iida Group Holdings and Osaka Metropolitan University, was designed by a master of the centuries-old textile art, but the painstaking work of applying it to a building fell to Taiyo Kogyo.

‘Converting a textile intended to be worn by people into a construction material was incredibly tough,’ says Nohmura. ‘We had to figure out how to make it resistant to the elements while retaining the distinctive matte appearance and texture of Nishijin-ori.’

Affixing the textiles to the building’s curved surface caused more headache. ‘The alignment had to be just right, because even a tiny error would cause the floral pattern to look off on the finished building,’ Nohmura says. ‘But after many sleepless nights, we managed to make it work.’

Days of wonder

Having spent all that time behind the scenes in Osaka, Nohmura is the ultimate Expo insider. Despite being in the building business, his favourite part of the massive event isn’t any specific pavilion or exhibition – it’s the daily programme of ‘national days’ organised by the participating countries.

‘The national days are amazing, since you get to see a different country put on a proper festival every day,’ he says. ‘They feature top-level artists and performers, and you really get a feel for the organising country’s culture.’

And don’t forget about all the amazing food. ‘If I could, I’d like to eat everything [available at the Expo],’ Nomura laughs. ‘Each country has brought its own chefs over, and they’re putting some serious effort into the food. Just eating your way around all the pavilions makes for a great experience.’ Pair that with a sauna session, and you’ve got yourself an Expo day to remember.

Reservations for the Taiyo Tsubomi saunas can be made through the Expo 2025 digital ticket site. See here for more info on how to purchase Expo tickets.