CityMakers Voices No.2 — Loreta Castro Reguera

In April 2026, Castro Reguera and Ambrosi were named winners of the 19th Global Award for Sustainable Architecture™ in Istanbul. Castro Reguera is a two-time Holcim Foundation Awards Gold winner. With UNAM's Manuel Perló Cohen, she took the regional Gold in 2017 and the Global Gold in 2018, both for Hydropuncture: La Quebradora Waterpark in Iztapalapa — a publicly-accessible water retention and treatment complex. She has since chaired the Holcim Foundation Awards 2020 jury for Latin America, joined the 2025 Awards jury, and served on the foundation’s Board.

Her experience places her at the forefront of sustainable design and construction, making her a suitable voice for the Holcim Foundation's CityMakers Voices series. In the conversation that follows, Castro Reguera traces how a resilient body of work has accumulated, how it is positively impacting Mexico City, and what other cities might take from it.

What do you see as the biggest opportunity in cities for your profession?

I can only really speak to my own city, and I think of Mexico City as the best ground for opportunities in design and urban design. It has always been a beautiful city. At some point, there have been decisions that maybe were not the best, but in my very particular view, I see Mexico City as a garden. It was conceived as a garden, and I still see that potential. Everybody in the city loves gardens — it is in our DNA. As I was telling you about that town with water, this idea of the garden, of the water garden, is so embedded into the city that I think, little by little, it will become that. A garden. A water garden city.

Tell us more about Mexico City’s relationship with water.

Mexico City is essentially built on a lake. The first city, Tenochtitlan, was built with great care, considering the natural context — understanding how to build land with silt from the lower part of the lake, then building canals to disperse water as it rose.

But we have had many different political periods since then, and when the Spanish conquest happened, and these Renaissance cities were imposed on the American settlements, they came with a disregard for context. That is when the problems started, because we stopped being flood-resilient. The "great solution" was, instead of building resilience, to desiccate the lake system. So now it is a city built in the center of a lake where water is hidden, served by an enormous drainage system whose job is to drain that lake every day. 

A lot of your work is about restoring harmony with nature and the urban fabric. How have you achieved this in your city?

We have thought a lot about this and have decided to focus on the neighborhood scale for many reasons, but the most important ones concern implementation. Larger systems require substantial budget and political will, whereas smaller, more acupunctural interventions do not necessarily require that much power to be implemented. On the other hand, they are very powerful once they start working — and that is what we have seen.

We started with one project. Once it was there and started working, it informed the others. Now it is us doing this kind of work, but also many other architects and urban designers are putting up these types of solutions in Mexico City.

The question we are asking is: how— by understanding the soil and the topography it sits on — can public space become more than just public space? How can it become natural, resilient infrastructure? The aim is to use what is there, the capacity of the ground and of the place itself, to manage water without any additional technologies.

How are you seeing your work catalyzing more projects?

We really saw the positive domino effect with our most recent project, which was not government-funded. A community asked us to stop flooding on the main road of their area by holding water in the town rather than sending it to the drainage system. That was the request. They gave us a site that was communally owned. We thought, ‘okay, we can build a water-retention infrastructure here,’ but they also wanted the site to become a place for the community — a community catalyst, a place of reunion. So we took the idea of sustaining water and reused that runoff to make a water feature for the community. It became a public pool, with a communal kitchen, public toilets, and showers. In the end, retaining water became retaining water for people.

It is a recent project, but it has been performing well since last summer, when we had very heavy rainfall across the Valley of Mexico. It has been very successful. We now know how much water this system can hold, and the floods are no longer happening. What is important is that this community-based project was obviously seen by the government. Last month, the senator of the area came to visit, amazed that there was no longer a flood on that road, and now the government wants to implement more of these types of projects.

What needs to happen for more communities to take this kind of ownership of the problems in their cities?

When a community is suffering a flood or has suffered an earthquake, they are all very prone to receiving solutions. That is not the best way for things to happen, but it is a way.

Beyond that, it is about understanding each other. There is always a political dimension, and that is often where the clash occurs — one party wants one thing, the other wants something else. That is where the role of the architect becomes important: first, by integrating someone who specializes in community management. We do community management as architects, but there are experts in this field who can help guide the process. Second, by being very close to the people who will be using these places. Really put yourself in their shoes and understand what is difficult for them.

Right now, for example, we are working in a small neighborhood that floods at least once every year. The insurance company simply replaces whatever gets damaged, and the next year it has to replace it again. I started thinking — what if we just raised their homes? We do not make them retreat because they have made the place their own. We make them understand, through architecture, how their homes can stop being damaged every time it rains. Raise them where they already are. When you start linking ideas like that, you do not have to move — you only have to move up. Of course, challenges arise. Where do you park the car, for example? There are practicalities to discuss. But getting in touch and listening matter. Being the one who brings up the solution together, rather than the one who imposes it, is always the best way. 

This interview is part of CityMakers Voices, a conversation series from the Holcim Foundation that gathers the thinkers, designers, and decision-makers whose work shapes the cities we live in. They form part of CityMakers, a new resource focused on the people, places, and programs revitalizing the urban realm.