The Shibamaruyama tomb mound is one of the largest keyhole-shaped tomb mound in the Metropolitan Area. It is located on a tip of a plateau including the Shiba park, at an altitude of about 16 m. Its rectangular mound portion heads for the south-southwest, and as per size, it is about 106 m long in total, with its circular portion having a diameter about 64 m, its rectangular mound portion a width of about 40 m at the end and a narrowed portion a width of about 22 m.

Several circular tomb mounds located around were dug away together with the plateau in the Edo Period and later, and a portion of the Shibamaruyama tomb mound was left. The original contour underwent substantial changes, in particular a top of the mound and the west side of the circular portion have been taken off. In 1898, Dr. Tsuboi Shogoro of the Tokyo Imperial University, a pioneer in archeological studies in Japan conducted excavations, and at that time, the main body (burial facility) which is believed to be located in the center of the circular portion had been already lost, and circumstances on the body/-ies and burial accessories are not known, except an existence of clay figures.

A construction of the mound is estimated to date back to 5th century, on the grounds of the narrow and low shaped rectangular mound portion, as well as land use. The mound is believed to be a tomb of one of the most powerful and wealthy families in Minami-Musashi (covering the areas of today's Tokyo and Kanagawa Pref.).