The 15657 / 15658 Brahmaputra Mail is a daily train that connects Old Delhi with Kamakhya in Assam. Introduced in 1972 after the construction of the rail section of the Farakka Barrage, the train originally ran as the Tinsukia Mail between Delhi Junction railway station and New Bongaigaon railway stations, with onward metre-gauge connection by a train of the same name numbered as 7Up and 8Dn to Guwahati and Tinsukia in the Indian state of Assam. From Wikipedia