Quicksilver, Barcelona, Spain. At first glance this appears to be like any fountain, but the difference soon becomes mesmerizingly clear: this isn't water, it's mercury, the only metal that is fluid at room temperatures.

Created by the artist Alexander Calder as a tribute to the mercury miners of Almaden, this artwork was unveiled in 1937 at the World's Fair in Paris. Its home is now the Fundació Joan Miró in Barcelona.

The way it moves and reflects the light is enough to keep my nose to the glass that encases it for quite some time.