Shiva Lingam, literally means phallus of Shiva (though it does not connotes this meaning for millions of the common devotees), is considered as an icon of Lord Shiva. Most Hindus worship it. The idols we have in our households are little ones; their size does not give a slightest hint of it being something obscene. On Haritalika, Hindu women’s festival when they observe fast and worship Shiva for the long life and wellbeing of their husband, my mother, and other women, used to bring fine wet sand from the river and make a Shiva Lingam from it. In fact, I first noticed this phallusy meaning only when I grew up and read about it in scholarly books.
This one was an exception. This I saw yesterday, made of ice, during Ram Navami observations, and I must say the most phallus-ish Shiv Lingam I have ever seen!
The curious ones have an article on Wikipedia.