The Narmada is closely associated with Lord Shiva. Naturally formed smooth stones called banas, made of cryptocrystalline quartz, are found in Narmada which are known as Shivalingas; the rare and unique markings on them are regarded by shaivaites as very auspicious. The Brihadeeswara Temple in Thanjavur has one of the biggest Bana Shivalingas.
The lingam (also, linga, ling, Shiva linga, Shiv ling, Sanskrit लिङ्गं, liṅgaṃ, meaning "mark", "sign", "inference" is a representation of the Hindu deity Shiva used for worship in temples. Hindus consider the lingam as a mark or sign of the presence of Lord Shiva, who at his highest level is perceived as limitless and formless.