The Kolkata Metro completed its maiden run under the river Hooghly on April 12, 2023 through a 520-metre tunnel under the river. Twin tunnels of 520 meters each, 13 meters below the river bed, connect Mahakaran (BBD Bagh) on the east bank of the Hooghly to Howrah station on the west bank. Howrah station is the deepest metro station in India at 33 meters below the...