The Prince of Wales has opened an "ultra-low carbon sustainability hub" at the University of Cambridge.
The Entopia Building is the new HQ for the university's institute for sustainability leadership.
Prince Charles, who has been a patron of the institute for more than 30 years, unveiled a plaque on the building on Regent Street in Cambridge.
Clare Shine, chief executive of the institute, said the site would support "sustainable development".
"We're creating new bridges between entrepreneurs, small and medium-sized enterprises and the most powerful actors in the economy, to put their collective weight and innovation capacity at the service of inclusive and sustainable development," she said.
"We hope to embrace fresh perspectives and forge solutions that work for people, nature and climate."
The new HQ is a retrofitted 1930s telephone exchange, with the project costing £12.8m.
It was funded by a £6m donation from greentech leaders Envision Group and a £3m grant from the European Regional Development fund, as well as the university investing its own money.
The prince also visited King's College in the city to meet seven students who were recipients of the HRH Prince of Wales Commonwealth Scholarships.
Prince Charles has been patron of the Cambridge Commonwealth, European and International Trust, which supports international students from member countries of the Commonwealth who wish to study at Cambridge, since 2010.
He asked student Paul Muiru, from Kenya, who is completing a PhD in history: "Are you pursuing the wonderful Kenyan tradition of running?
"You always win all the marathons.
"Unbelievable, incredible."
Mr Muiru, 40, said afterwards that it was "very exciting" to meet the prince.
"I was nervous but a very good moment, memorable," he said.
"I'm glad to have met the prince.
"He's very intelligent, I love him."
Prince Charles then visited the Whittle Laboratory to learn about work to achieve net-zero aviation.
Business Secretary Kwasi Kwarteng was also at the laboratory and said it was "fantastic" to accompany the prince.
"We are determined to seize the economic opportunities of the global shift to greener aviation technologies, which will help to secure growth and thousands of jobs across the country," Mr Kwarteng said.
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