Ancient Stone Lingam (aka Linga) in one of the Po Nagar Cham Towers (Nha Trang, Vietnam)
The Lingam (also, Linga, Shiva linga Sanskrit लिङ्गं liṅgaṃ, meaning "mark," or "sign,") is a phallic symbol for the worship of the Hindu deity Shiva.
See more information on Wikipedia: Lingam .