There are hundreds of caves in the Eocene formations of the Shephelah. The "Bell Caves" are so-called because of their unique shape that is a result of the method used in quarrying them. As the dug down, eventually one "cave" broke into, and overlapped another cave.
First, a round shaft, no more than three feet in diameter, was carved through the hard Nari surface rock—see the top of the photograph. The soft chalk layers beneath the Nari was then cut into blocks and removed with ropes through the opening at the top. The quarrying took place vertically and horizontally—thus giving the "cave" its distinctive bell-shape—see photo!
The quarrying began at the end of the Byzantine period (ca. seventh century AD) and reached its height in the Early Islamic period (to the eleventh century AD). The chalk blocks were used in construction and in the production of lime. Thus, Beth Guvrin was an important chalk-supply center during those periods.
the 10th-century Arab traveler al-Muqaddasi wrote of Bet Guvrin: "is is a land of richness and plenty, and in it are many marble quarries . . . ."