Visitors came from across the Channel to view the green credentials of one London office building.
Politicians from the French city of Rennes came to Southwark to see the Borough’s new council offices at 160 Tooley Street.
The council, along with that of Rennes, is part of a Europe wide scheme which plans to tackle climate change through the better use of energy.
The offices have such design features as rainwater recycling, solar heating and movement-sensitive lighting, and it is hoped the new designs will save the up to 20 tonnes of carbon emissions every year.
A council spokesman said: “We’re very pleased to be able to host these guests from Rennes.
“We hope that by sharing our experiences and aims we can all tackle the challenges of climate change in the future.”
In total, the council hopes to be able to reduce emissions by 80 per cent by 2050.