“How often do we walk through a place without ever wondering what lies beneath it?”

I’ve walked across Campus Hönggerberg many times. Like most people, I admired the architecture, hurried between buildings and associated innovation with laboratories, artificial intelligence and groundbreaking research. It never occurred to me that one of ETH Zurich’s most fascinating innovations wasn’t inside a laboratory at all. It was beneath my feet. When I joined the Anergy Grid Tour (German: Anergienetz), I expected to learn how buildings are heated and cooled. Instead, I left seeing the campus in a completely different way.

There is another ETH beneath the one we know

Walking through the underground technical corridors felt like entering a hidden city. Instead of lecture halls and cafés, I found pumps, pipes, heat exchangers and control systems quietly working behind the scenes. It was easy to forget that only a few metres above us, campus life continued as usual.

One sentence stayed with me throughout the tour:

“Above ground, people exchange ideas. Below ground, buildings exchange energy.”

Suddenly, the campus no longer felt like a collection of individual buildings. It felt like one connected organism.

More than engineering

As Philipp Heitemann, one of the driving forces behind ETH Zurich’s Anergy Grid and the leader of its tours, guided us through the facilities, I realised this wasn’t really a story about technology.

It was a story about thinking differently.

Since 2013, ETH Zurich’s Anergy Grid has connected buildings through an intelligent low-temperature energy network. Instead of wasting excess heat, it stores thermal energy underground and redistributes it whenever another building needs it.

The technology is impressive. The philosophy behind it impressed me even more. Before the tour, I thought sustainability was mainly about producing more renewable energy. The Anergy Grid introduced me to another perspective:

Maybe the future isn’t only about producing more. Maybe it’s about wasting less. That simple idea has stayed with me ever since.

Coffee with Philipp

Before leaving, I asked Philipp a few questions that I couldn’t stop thinking about.

What do visitors almost always overlook during the tour?

“Most people focus on the technology. I hope they also notice the way of thinking behind it. The real innovation isn’t just the infrastructure—it’s the idea that buildings can cooperate instead of working independently.”

What’s one question you wish people asked more often?

“Instead of asking how the system works, I’d love more people to ask how we can transfer this way of thinking to entire neighbourhoods and cities.

“Imagine we’re standing here again in 2050. What do you hope we’ll see beneath our cities?

“I hope connected energy systems have become completely normal. The less people notice them, the better they’re probably working.”

Facts That Surprised Me

First in the world:The Anergy Grid went into operation in 2010 as the world’s first low-temperature anergy network—a pioneering concept that continues to inspire similar projects around the globe.

The ground is a giant thermal battery: Thermal energy can be stored underground for months and recovered when it’s needed.

Heat gets a second life: Instead of being wasted, excess heat is captured, stored and reused elsewhere in the network.

One network. Two seasons: The same infrastructure heats buildings in winter and cools them in summer.

Buildings work together: Instead of operating independently, they exchange thermal energy through one connected system.

Open source: The concept is openly shared, allowing cities, universities and organizations worldwide to build on ETH Zurich’s experience.

Curious? Join one of Philipp Heitemann’s Anergy Grid tours and discover the hidden world beneath Campus Hönggerberg.

Five Things I Took Home

• Innovation doesn’t always have to be visible.
• Great ideas often come from connecting existing systems rather than inventing new ones.
• Sustainability begins with systems thinking.
• Some of the smartest technologies quietly work in the background.
• Looking beneath the surface can completely change how we see the world above it.

Walking back across Campus Hönggerberg, nothing around me had changed. Students were still cycling between lectures. Researchers were still discussing ideas over coffee. The buildings looked exactly the same. Only my perspective had changed. Sometimes the most remarkable innovations aren’t the ones we immediately notice. Sometimes they’re quietly working beneath our feet. And perhaps that’s the most inspiring lesson I took home from the Anergy Grid Tour.

Visit ETH Zurich as part of a tour. Come along and discover what ETH Zurich has to offer, in ways that are as varied as our visitors themselves.