Also there are five circumferential roads forming a series of concentric semi-circular arcs around Manila. Other tubes have concentric and radial jointing features. Liquids are encapsulated by a rotating head containing concentric nozzles. This point becomes center of the concentric spherical shells. Pei's design was based on a circular tower with concentric rings. Moats forming roughly concentric circles were dug for further protection. Archaeologists postulate that houses were constructed on top of the concentric ridges. Soreness can theoretically be avoided by limiting exercise to concentric and isometric contractions. The logo of the GCC consists of two concentric circles. The temple is spread over a area, within layers of concentric courtyards. This is done by projecting each solid onto a concentric sphere. Inside each column were three concentric tubes. The users thus stand in the center of two concentric circles. Large groups allow for the creation of several concentric circles. Consider unwrapping the concentric circles to straight strips.