London landmarks are being illuminated by energy-efficient lighting to encourage Londoners to cut emissions.
The Tower of London, Tower Bridge, Southwark Cathedral, and 12 other buildings will be lit up on Thursday as part of Switched On London 2008.
The week-long event will also highlight the unnecessary lighting of office space at night in the area.
It will be audited for energy consumption to show it can provide better lighting using less energy.
Switched On London's team of lighting designers aim to demonstrate how expert design combined with utilising modern technology allows sustainable and creative lighting.
Mayor of London Ken Livingstone said: "Switched on London is to be commended for their campaign to promote the use of energy efficient lighting in London at night.
"By using more efficient lighting, organisations and households can save money and help to tackle climate change."