The Marabar Caves are a central aspect of the novel—a presence in the distance during the first section, the setting of the second section, and the shadow that looms over the third section. The caves represent an ancient, inhuman void, the more terrifying aspect of the universal oneness embraced by Hinduism. The caves themselves are domelike and pitch-black, with nothing beautiful or romantic about them. Inside, any sound—whether human speech or a fingernail scratching the wall—is reduced to a single echo that sounds like “boum.” This echo captures the essence of the Marabar Caves, as it shows the emptiness behind all human action. This is a kind of “unity” like that found in Hinduism, but it is a unity of chaos instead of one of love, as the caves seem almost alien and malicious, unfriendly to humans. Even the Indians of Chandrapore cannot act as real “guides” to them or explain them.
While in the caves, Adela and Mrs. Moore both experience some frightening aspect of life that they had not considered before. Mrs. Moore sees the smallness and hollowness of her Christian faith, and succumbs to a kind of irritable apathy after seeing the void the caves represent. Adela, meanwhile, is confronted with the reality of her lack of feelings for Ronny and then the horror of her assault. The attack is never fully explained, so it almost becomes an embodiment of the darkness of the caves.