Home Minister Rajnath Singh on Friday paid tribute to freedom fighters who spent years in Cellular Jail at Port Blair in the Andaman and Nicobar Islands."Paid tributes to those brave freedom fighters of India's Independence struggle who spent years in Cellular Jail of Andaman and Nicobar Islands," the minister tweeted.The Cellular Jail, colloquially known as 'Kala Pani', was a colonial prison used to exile freedom fighters -- described by the British as political prisoners -- to the remote archipelago. It is one of the murkiest chapters in the history of colonial rule in India.