• Steffen Lehmann and Igor Peraza both met when they worked together from 1990 to 1993 in Tokyo, at the studio of Pritzker-Prize winner Arata Isozaki, and since then have been practicing and teaching globally for the last 30 years.
  • In over 100 projects - through our built works - and in over 20 published books, we share insights into how architecture and urban design can make people healthier and happier. It is a thinking and approach to design that we apply to all projects.
  • Our work is research-informed and the mission is to create the world’s most sustainable urban design and architecture.
  • To best make use of our immense international experience, we follow four principles to creating a successful and resilient architecture culture: collaboration and teamwork, leadership in sustainable design, integration of research, and diversification of project types and places.

Steffen is Founding Partner and Principal of si_architecture + urban design
Professor of Architecture & Urbanism

It is hard to find anyone more loyal and client-focused than Steffen. He has dedicated his entire working life to helping clients and his major focus is to make sure a client’s business journey is a good one

Steffen is Founding Partner and Principal of si_architecture. Born in Stuttgart (Germany), he is a Professor of Architecture at the University of Nevada, Las Vegas, where he is also the Founding Director of the Urban Futures Lab. In recognition of the international significance of his work, he was appointed as chair holder of the inaugural UNESCO Chair for Sustainable Urban Development in the Asia-Pacific. He was Head of two schools of architecture, Founding Director of three successful research centers, and Principal Investigator of several large multidisciplinary grants, generating over $15 million in research grants.

Steffen has advised over a dozen of cities on sustainable urban development, including Berlin, Stuttgart, Shanghai, Singapore, Sydney, Melbourne, Adelaide, Brisbane, Abu Dhabi, Ho-Chi-Minh City, Oslo, Helsinki, Brighton and Reno. He became a licensed architect in Berlin in 1993 and founded Steffen Lehmann Architekten BDA as a collective interdisciplinary practice.

His firm in Berlin designed and built a construction budget of $1b, and was actively involved in the urban creation of the 'New Berlin'. He has many years’ teaching experience as full professor and as tenured professor at the University of South Australia and University of Portsmouth; and visiting professor at the TU in Berlin and Munich, NUS Singapore, and UC Berkeley.

  • Ph.D. in Architecture & Urbanism, TU Berlin, Germany
  • AA Diploma, Architectural Association School, London
  • Dipl. Ing., Mainz University of Applied Science, Germany

  • 2020- Founding Principal, si_architecture + urban design
  • 1993-2020 Founding Principal, Steffen Lehmann Architekten
  • 1996-2002 Project partnership as Generalplaner with Christian de Portzamparc
  • 1990-1993 Arata Isozaki & Associates, Tokyo
  • 1988-1990 James Stirling, Michael Wilford & Associates, London

Igor is Founding Partner and Principal of si_architecture + urban design
Professor of Architecture Practice

Friends and clients appreciate how approachable and easy Igor is to talk to. His biggest enjoyment is getting a positive outcome where a client does not think this is possible.

Igor is Founding Partner and Principal of si_architecture. Born in Caracas, he is a Professor of Architecture Practice at the American University of Sharjah, UAE; and a Transformation Fellow at the School of Architecture at UNLV in Las Vegas, teaching the Mexico-City and Barcelona Global Studios. For many years, Igor was a project director at EMBT in Barcelona. He worked for five years at the Atelier of Arata lsozaki in Tokyo, where he met Steffen in 1990. At Isozaki Atelier, he led the Domus (Museum of Mankind) project in La Coruna, Spain.

In 2000, he relocated to Barcelona to work with Miralles Tagliabue EMBT as Director of the award-winning Santa Caterina Market project. He subsequently served as Director of EMBT's Shanghai office, where he led a number of highly innovative projects, including the Spanish Pavilion at the 2010 World Expo. He became a licensed architect in Barcelona in 2000. He has many years’ teaching experience and has previously taught at the Polytechnic University of Catalonia, the European Institute of Design, Tongji University in Shanghai, and the Lebanese American University in Beirut.

  • Ph.D. in Architecture, Kumamoto University, Japan
  • M.Arch., Hokkaido University, Japan
  • B.Sc., Universidad Central de Venezuela y Caracas

  • 2020- Founding Principal, si_architecture + urban design
  • 2009-2013 Director, EMBT Shanghai Office
  • 2008-2009 Miralles Tagliabue EMBT, Barcelona
  • 2004-2008 Igor Peraza IMQ Architects, Barcelona
  • 2000-2004 Miralles Tagliabue EMBT, Barcelona
  • 1996-2000 César Portela Architects, Galicia, Spain
  • 1990-1996 Arata Isozaki & Associates, Tokyo


si_architecture stands for interdisciplinary collaboration and teamwork. No matter the scale of the project, we put the best minds together to push the creative and technical limits of what’s possible.

Fortino Acosta, M. Landscape Arch., Ph.D. Candidate

Fortino is instrumental to the Dubai office of si_architecture. Born in Mexico City, he holds a M.A. in Landscape Architect from the University of Sheffield, and a B.Sc. in Industrial Engineering.He has gained varied practical experience in different countries, and taught urban design studio at UNLV and Ibero University. Fortino is passionate about sustainable urban design, landscape design and public space. He speaks English, Spanish and Portuguese.

David Paz, B.Arch.

As a design strategist, David leverages his digital expertise and skills to drive innovative projects. He was born in Madrid and holds a B.Arch. from Setsunan University in Osaka, Japan. He did additional training at Harvard University GSD and at the ETH Zurich, and has worked for several years as an architectural designer in Japan and Spain. He speaks English, Spanish and Japanese, and works collaboratively with all members of the team.

Mary Krajekian, B.Arch.

Mary excels in merging aesthetics with functionality and is passionate about the sustainable design of mixed-use commercial projects and high-end residential buildings as well as urban design. She grew up in the UAE, studied at the American University of Sharjah and in Barcelona, and knows the Arab region well.

Alina Sebastian, B.Arch.

As a talented architectural graduate, Alina has a breadth of important skills ranging from conceptual planning and design to project management. She grew up in the Middle East, studied at the American University of Sharjah and Barcelona, and knows the Arab region well.


“We are pleased to provide a very positive reference for si_architecture + urban design and recommend their services. They provide professional, confident leadership from the initial design through construction, and I believe the exceptional architectural and urban design, their responsive and diligent commitment to client satisfaction, and the professional attitude and integrity are the main reasons why clients chose to work with them.”

Her Excellency Dr. Shaikha Al Maskari, Chairperson of the Board, Al Maskari Holding

Abu Dhabi, UAE

“What an amazing journey it has been over a period of ten years! The architects were involved in the creation of the new city centre for the formerly divided city of Berlin, from the first vision to the final opening of the new Potsdamer Platz district. They are urban strategists with a real passion, and their practice is an urban strategy powerhouse that always inspired and met our very high expectations.”

Dr. Manfred Gentz, Chairman, Debis Immobilien Management

Stuttgart, Germany

“Their unique selling point is being able to think outside the box when assessing a complex design challenge. Steffen was key to the design and delivery of our new headquarters in the centre of Berlin, a building with high-performance workplaces for 500 people at the Association of German Banks. The architects developed a genuine rapport with the BdB as their client, and we trusted them to do the right thing. Their direct approach is refreshing and Steffen puts himself in his client’s shoes, which is always of great benefit. They designed and executed our new collaborative headquarters in Berlin that our employees, members and clients enthusiastically love being in.”

Dr. Manfred Weber, General Executive Manager & Member of the Board, Bundesverband Deutscher Banken

Berlin, Germany

“The architects were very helpful and reliable, providing us with critical insight into our construction project and provided innovative solutions. We appreciated their down-to-earth attitude and ability to explain complex things clearly. Despite the very challenging budget situation, they managed the project as Generalplaner and created a beautiful new embassy and residence at Pariser Platz, in the heart of the city.”

Claude Martin, Ambassador of France to Germany


“We have been working with Steffen on urbanisation, sustainable development and environmental design issues for several years. He has been a member of our advisory group and his critical knowledge on future cities and research in sustainable urbanism always attracts keen interest and attention. We highly appreciate his tireless and constant contributions to the vision of Adelaide’s more sustainable future. As a city, it is important for us to have new approaches and access to cutting-edge research and knowledge that supports our daily work.”

Stephen Yarwood, formerly The Hon. Lord Mayor

City of Adelaide, Australia

“As curator and artistic director of the Laneways projects, which involved twenty collaborating teams of artists and architects to design and built temporary installations in the urban public space of Sydney’s city centre, Steffen managed the entire project. It was a huge success, and one of the works became a permanent installation. We had always the confidence that everything has been dealt with, and overall it was a good collaboration alongside out team.”

Clover Moore, The Hon. Lord Mayor

City of Sydney, Australia

“It was a great pleasure working with Steffen and Igor – their diligence, hard work, and understanding throughout the process was greatly appreciated and made our work easier than it might otherwise have been. They are easy to work with and at the same time laser-focused. We look forward to working together again. Thank you very much for the amazing collaboration! The consortium is very pleased with everything produced and we hope we can continue to develop new interesting synergies and projects in the future.”

Dr. Daniela Melandri & Dr. James Taplin

EU Research Funding Manager, Future Cities Catapult & Research Lead ‘Urban Living’ | Innovate UK

“Over the last ten years, Steffen has shown outstanding leadership in advising our organisation and the City of Helsinki and the Helsinki Metropolitan Region concerning future urban development. He has an international and well-established reputation as leader in Green Urbanism and we have invited him several times to contribute to our urban strategies and hold seminars. His work and visits to Helsinki have not only made a significant contribution to the field of sustainable urban development, but has shaped and continues to shape our thinking about the future of our metropolitan region.”

Irma Karjalainen, Director

Helsinki Region Environmental Authority, Finland

“Steffen and Igor have more than 30 years of leadership experience in practice and a distinguished and widely recognized 20-year career in academia. I am impressed with their enthusiasm and passion for architecture, their many accomplishments, and their unparalleled international experience.”

Dwayne R. Eshenbaugh, President AIA Nevada

President AIA Nevada, USA