The Floating ecopolis, otherwise known as the Lilypad, is a model designed by Belgian (not French as the article says) architect Vincent Callebaut. The 'Floating Ecopolis for Climate Refugees' was a concept design proposed in 2008 to deal with the effects of global warming as the polar ice caps melt and oceans rise; displacing land fairing inhabitants along the coast.
The Lilypad doesn't just rise up and down with the tide. Callebaut wants the entire city to be able to float all around the world, moving on natural ocean currents. Callebaut says his lily pads can hold up to 50,000 people.