Yagura in Japanese is a watch-tower or turret. In Kamakura, however, Yagura are caves where cremated remains of samurai and priests were often buried. The Kamakura Shogunate forbade to dig graves or place tombs in the open fields in 1242 as the flat space was scarce. Since then, people had to bury ashes digging caves at hill sides. The soil in Kamakura is mostly tuff and digging a cave was rather easy. Once an opening was made, ashes were placed in one of the several niches dug on the floor or wall inside the cave. In other words, caves were basically graves, and Gorinto and/or Hokyo-into were placed. On the walls of caves, Sanskrit letters are usually engraved, most of them meaning Amitabha, though unable to decipher. Those who were buried there were mostly from the upper-class families. Exactly how many yagura exist in Kamakura is unknown, but the number is said to be no less than 4,000. Most noted among them are those on the hill behind Kakuonji, which is popularly called 108 yagura. (There are 177 to be precise.) Behind Zuisenji are 79, and 56 are located near Jomyoji. Since those are not accessible for occasional visitors, the easiest way to see them is to go behind Jufukuji, where typical yagura including that of Masako Hojo and Sanetomo Minamoto are found in the graveyard (picture; left).
During the 150-year Period, Kamakura maintaining a population of 20,000 must have produced 100,000 dead people on the assumption that their average life-span was 30 years. How could they deal with the corpse in such a small area? A cave may have housed 20 remains at best. Others were sent into sea and valleys.
Source: Yagura (A Guide to Kamakura)