The first bridges have been lit up as part of a design contest to illuminate the River Thames across London.
Up to 15 crossings will eventually become part of Illuminated River, thought to be the longest public art commission in the world.
New lighting - with connected LED patterns - now adorns London, Cannon Street, Southwark and Millennium bridges.
The privately-funded work is expected to stay for at least 10 years.
When complete, Illuminated River will cover a total of 4.5 nautical miles (8.3km) of the Thames.
The new lighting is designed to co-ordinate London's bridges, with old lights replaced with new LEDs that will switch off at 02:00 BST in order to reduce energy consumption.
The Illuminated River Foundation charity raised funds to install and maintain the lighting.
The only public funding has been £250,000 of "seed funding" from City Hall for the initial competition, while the City of London Corporation paid to replace the light fittings on London Bridge.
The design was created by American light artist Leo Villareal and British architects Lifschutz Davidson Sandilands, who were influenced by the palettes of Impressionist and English Romantic painters.
"I'm hoping to follow in the footsteps of Monet, Turner and Whistler and reveal the truly unique, inspiring and poetic character of the Thames," Villareal said.
Hannah Rothschild, who was behind the idea, said the project "will transform a snake of darkness into a ribbon of light".
It is hoped the next five bridges will be illuminated by autumn 2020.
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