Líneas de Nazca
Similar pictures exist elsewhere in the world, notably the far larger Nazca Lines in Peru, which are on flat land but visible from hills in the area. However these were made in desert terrain rather than on grassy hillsides, so have not become overgrown and thus have survived much longer without maintenance. The Nazca Lines were formed by removing loose stones from the lines to expose the whiteish underlying soil, which is not itself dug.