These are portable prehistoric drawings of animals, etched into rock by the sketchers around 18,000 years ago. They can be found in the Museum of Prehistory in Valencia and are from the Cave of Parpalló . The lines are cut into limestone rock and sometimes painted as well as etched. 5000 of these pictures were found in the cave, many but they span an era of about 17000 years. These works can be passed between people, moved around, travelled with, kept, and held in a way the wall paintings cannot.
Kurt Schwitters also needed art of a similar scale that could be carried around easily and created with minimum tools. He made some portable art when he was travelling to Britain on an ice-breaker as he fled the Nazi invasion of Norway. He carved hand sized sculptures from birchwood.