At seven locations along the Iparraguirre Kalea, in Bilbao, seven diamond-shaped openings in the pavement provide passers-by a glimpse into an evocative world beneath their feet. Peering into the openings, viewers see a spectral form that is at once geometric and organic, a shape with the texture of a mineral and the sharp clear edges of a polyhedron. These forms are in fact illusions produced by simple kaleidoscopes inserted into the ground. Each consists of four abutting mirrors that taper to a point. Precise cuts have been made from the tips to produce a geometrical shape in the accumulated reflections, with a different shape featured in each. 

At the heart of the artwork are seven types of stone that tell the geological story of Bilbao. The city has been a major centre of mining over the centuries and all seven types of stones originate from the earth nearby – calcite, limonite, Goethite, siderite, green basalt, sandstone, and limestone. The clusters of stones are reflected by the mirrored walls of the kaleidoscopes, lending the geometrical forms that arise a diversity of textures, colours, and materials.