Between Dibrugarh and Lakhimpur Districts, the river divides into two channels—the northern Kherkutia channel and the southern Brahmaputra channel. The two channels join again about downstream, forming the Majuli island, which is the largest river island in the world. At Guwahati, near the ancient pilgrimage centre of Hajo, the Brahmaputra cuts through the rocks of the Shillong Plateau, and is at its narrowest at bank-to-bank. The terrain of this area made it logistically ideal for the Battle of Saraighat, the military confrontation between the Mughal Empire and the Ahom Kingdom in March 1671. The first combined railroad/roadway bridge across the Brahmaputra was constructed at Saraighat. It was opened to traffic in April 1962.