A pyramid (from Greek: puramis pyramis) is a structure with triangular outside surfaces that converge to a single step at the summit, giving the shape the shape of a pyramid in the geometric sense. A pyramid's base can be trilateral, quadrilateral, or any polygon form. The three main types of pyramids are the plain, the stepped, and the crowned. Plain pyramids have flat tops without sideskips. They can be made of solid material or of hollow construction. Solid-top pyramids require very strong materials to support their weight, while hollow-necked ones tend to be much more flexible. Stepped pyramids have two or more levels, with each level being a horizontal slab supported by pillars or walls rising from the ground floor to the crowning wall or roof on which they are placed. The number of steps varies depending on their purpose but generally there are between 3 and 8 levels. Crowned pyramids have a top shaped like a capstone used to finish off one end of a building or monument. They usually weigh less than 200 kg (440 lb). Pyramids have been built since ancient times using various techniques but mostly by dry stone masonry carried out by workers called "masons". Pyramids were originally constructed as tombs for important people such as kings or priests. In this case, the aim was to provide a place for the body to rest in peace, without contaminating it with weapons or tools.