At the centre of Volvelle lies the island of Seili, surrounded by a spiral that unfolds outwards through hours, days, months, years, and cultural and geological eras, all the way back to the formation of the Earth. The inner discs rotate and feature openings. When the inner discs are aligned with the time of observation, the openings fall into positions that reveal information about the meadow in question at the time of observation.
The observation periods are colour-coded. Yellow represents early summer, red early summer, green mid-summer and purple late summer. Plants marked with a yellow circle therefore flower in early summer, those marked with a green circle in early summer, and so on. Each plant also represents a particular period in natural or cultural history. The lines connecting the edges, gaps and circles of the discs indicate which plants were in flower at the time of observation.
