in most works on rock art, which concentrate on engravings and paintings by prehistoric peoples. A few such works exploit the natural contours of the rock and use them to define an image, but they do not amount to man-made reliefs. Rock reliefs have been made in many cultures, and were especially important in the art of the Ancient Near East. Rock reliefs are generally fairly large, as they need to be to make an impact in the open air. Most have figures that are over life-size, and in many the figures are multiples of life-size. Stylistically they normally relate to other types of sculpture from the culture and period concerned, and except for Hittite and Persian examples they are generally discussed as part of that wider subject. The vertical relief is most common, but reliefs on essentially horizontal surfaces are also found. The term typically excludes relief carvings inside caves, whether natural or themselves man-made, which are especially found in India. Natural rock formations made into statues or other sculpture in the round, most famously at the Great Sphinx of Giza, are also usually excluded. Reliefs on large boulders left in their natural location, like the Hittite İmamkullu relief, are likely to be included, but smaller boulders may be called stelae or carved orthostats. Earth figures Earth figures are large designs and motifs that are created on the stone ground surface. They can be classified through their method of manufacture. Intaglios are created by scraping away the desert pavements (pebbles covering the ground) to reveal a negative image on the bedrock below. The best known example of such intaglio rock art is the Nazca Lines of Peru. In contrast, geoglyphs are positive images, which are created by piling up rocks on the ground surface to resulting in a visible motif or design. Motifs and panels Traditionally, individual markings are called motifs and groups of motifs are known as panels. Sequences of panels are treated as archaeological sites. This method of classifying rock art however has become less popular as the structure imposed is unlikely to have had any relevance to the art's creators. Even the word 'art' carries with it many modern prejudices about the purpose of the features. Rock art can be found across a wide geographical and temporal spread of cultures perhaps to mark territory, to record historical events or stories or to help enact rituals. Some