Ryugu has a round shape with an equatorial ridge, called Ryujin Dorsum. Ryugu is a spinning top-shape asteroid similar to Bennu. The ridge is shaped by strong centrifugal forces. The western side has a different shape compared to the rest of the asteroid. The western side, also called the western bulge has a smooth surface with a sharp equatorial ridge. The models showed that subsurface material is structurally intact and relaxed in the western bulge, while other regions are more sensitive to structural failure. The eastern and western side of Ryugu are bordered by the Tokoyo and Horai Fossae. The structural differences are due to structural changes in the history of the asteroids. Landslides and internal alternations reshaped the asteroid during a phase of high speed rotation. The western bulge is the region that was not affected by these reshaping forces.