There is this park in the center of Paris called the Jardin du Luxembourg. People go there to jog, relax, picnic... And children love that place. One of the only "green" place in the center of Paris... Though it really has nothing like those huge parks in the center of London.
Anyway, recently France was commemorating the end of slavery. There were shows on TV, and cultural events about it. In the Jardin du Luxembourg they've installed bamboo plants, blue sand and pictures on a special cloth in the entrance of the park to remember.
I think it is supposed to make you think of the sea.