Konkrete kunst

The term konkrete kunst (concrete art, not the art of concrete!) was first introduced by Theo van Doesburg in 1930 and developed in the following decades by various artists, most notably Max Bill.  This form of abstraction rejects any symbolical association with reality.  Nothing is more concrete than lines or colours.  There are a few art museums in Germany specialized in konkrete kunst, including Museum für Konkrete Kunst in Ingolstadt:

Bridget Riley at Museum im Kulturspeicher, Würzburg 2010:

Josef Albers at Josef Albers Museum, Bottrop 2010: