“WOW, it looks like a Greek temple!” “Do they really pool rainwater here?”

These are common reactions from first-time visitors to the Metropolitan Area Outer Underground Discharge Channel, an enormous subterranean flood control facility located beneath Kasukabe City, just north of Tokyo.

Towering 18m-high pillars support the vast chamber 50m below ground, giving it the nickname “the underground temple”.

It’s not just impressive architecture.

Stretching 6.3km and capable of holding 670,000 cubic metres of water – roughly the volume of a 60-storey skyscraper – the channel plays a vital role in protecting Tokyo from floods.

Since its completion in 2006, it has saved an estimated ¥148.4bil in potential flood-related damage, according to Japan’s Ministry of Land, Infrastructure, Transport and Tourism. That’s a 65% return on the initial ¥230bil investment – and counting.

But its real value lies in peace of mind. Residents in flood-prone areas of Kasukabe no longer need to worry each time heavy rain is forecast.

For countries like Indonesia, where over five million people were affected by floods in 2024 alone, such infrastructure could be transformative.

In Jakarta, annual flooding is almost routine due to the city’s topography, intense monsoon rains and limited drainage capacity.

With high-density traffic and little room for large surface-level construction, a Tokyo-style underground shield-tunnelling method – which allows digging without closing roads – could be the ideal solution.

Environmental accolade

Tokyo’s environmental initiatives have earned it global recognition.

In the 2024 Global Power City Index, Tokyo ranked third overall (behind London and New York), and stood out as the only Asian city in the top 10 for “Commitment to Climate Action”, a new benchmark under the Environment function.

This accolade stems from years of consistent, multi-layered urban planning – the kind that South-East Asian cities, now grappling with climate-related challenges, can learn from.

Rooftop forests, greener skylines

High above ground, Tokyo has also been reclaiming the skyline for nature.

Perched atop Ginza Six, a landmark building in the city’s upscale shopping district, is a lush 4,000sq m rooftop garden.

It features a circular promenade where office workers and shoppers stroll under the open sky, soaking in views of Tokyo Tower and the Ginza streets below.

The green rooftop, the largest in the district, was created in 2017 as part of Tokyo’s aggressive urban greening policy.

The goal? Combat the urban heat island effect, improve air quality and beautify the cityscape.

Since 2001, the Tokyo metropolitan government has required all new buildings over a certain size to dedicate at least 20% of their ground-level open space and roof space to greenery.

Since April 2025, solar panels have also become mandatory on all new homes – a significant step toward reducing carbon emissions in the housing sector.

This is where South-East Asian cities can catch up.

Bangkok, for instance, routinely suffers from hazardous levels of air pollution.

In January 2025, 48 out of Bangkok’s 50 districts recorded PM2.5 levels exceeding 75 micrograms per cubic metre – well above Thailand’s own limit of 50, let alone the World Health Organisation’s safer guideline of 25.

The root cause? A national power mix heavily reliant on coal and natural gas.

While a full transition to renewables will take time, measures like Tokyo’s – greening urban surfaces and decentralising solar power – are practical, affordable and adaptable today, even in cities like Hanoi or Ho Chi Minh City, which are also battling worsening air quality.

Doing away with waste bins

Another often-remarked feature of Tokyo is how clean its streets are – despite the near-total absence of public rubbish bins. This isn’t magic; it’s cultural. People simply carry their rubbish home.

That attitude is part of a broader commitment to waste reduction.

Tokyo aggressively promotes the three Rs – reduce, reuse, recycle.

Packaging must use recyclable or biodegradable materials. Plastic waste is sorted and processed into materials for chemical reuse. There are clear efforts to phase out single-use items and reduce landfill dependency.

Compare this with Malaysia, where landfills still dominate the waste disposal system and plastic pollution remains a critical issue. Or Indonesia and the Philippines, where marine plastic leakage is among the highest globally, largely due to the logistical challenges of collecting waste across thousands of islands.

Tokyo’s approach shows what’s possible with a combination of policy, infrastructure, corporate responsibility and public cooperation.

It’s not just about building recycling plants – it’s about building habits.

Mindset shift that makes it work

Perhaps Tokyo’s greatest environmental innovation isn’t technological or architectural – it’s psychological. Japan’s environmental policies don’t always land smoothly. Businesses worry about costs. Citizens worry about inconvenience.

But once new rules are implemented, many discover that they improve quality of life or even reduce operational expenses. Over time, resistance turns into acceptance – and eventually into pride.

That kind of collective mindset shift is the secret ingredient missing from many South-East Asian efforts.

Infrastructure projects and regulations can only go so far without public buy-in.

Tokyo’s experience proves that when residents are on board, even seemingly drastic environmental measures can succeed – and even thrive.

Lessons for South-East Asia

Cities like Jakarta, Bangkok, Kuala Lumpur, Manila and Ho Chi Minh City are facing rising environmental threats: floods, pollution, waste and extreme heat. And they’re doing so with fewer resources and in more complex social contexts than Tokyo.

Still, the Japanese capital’s experience offers a toolkit that can be adapted – a hybrid of engineering and behaviour change, of big infrastructure and small daily acts.

Whether it’s building stormwater megastructures beneath your feet or planting rooftop forests above your head, Tokyo is proving that a dense, bustling city can still be liveable, breathable and resilient.

It’s a message South-East Asia might find worth listening to – before the next monsoon or smog crisis hits. — AFP