The Howrah Maidan-Esplanade section underwater Metro line has the first transportation tunnel under a river in India. It passes under the Hooghly River – Kolkata and Howrah are situated on its east and west banks, respectively – and has the deepest Metro station in India at Howrah (30 m deep).

Ahead of the upcoming Lok Sabha elections, a total of 11.45 km is being added to the existing Kolkata Metro network– 5.4 km on the Orange Line, 4.8 km on the Green Line and 1.25 km on the Purple Line.

According to officials, from its inception in 1984 till 2014, only 27.99 km of the Metro network was functional in Kolkata. After 2014, the Metro network was expanded by 25.34 km, starting with the inauguration of the first phase of the East-West Metro from Salt Lake Sector V to Salt Lake Stadium over a 5.3 km stretch in 2020. Gradually, the Kolkata Metro extended its wings and the Salt Lake Stadium to Phoolbagan (1.67 km) and Phoolbagan to Sealdah (2.33 km) stretches were also opened for commercial service. The Noapara-Dakshineswar stretch (4.14 km) was inaugurated in 2021 and the Joka-Taratala (6.5 km) stretch on the Purple Line was inaugurated in 2022.

As per Metro authorities, 2022-2023 recorded the highest-ever Metro network expansion of 14.23 km in a single year. “It was an addition of 36 per cent to the existing network since Kolkata Metro’s inception,” an official said.

Between 1972 and 2014, an expenditure of Rs 5,981 crore was made for all Kolkata Metro projects.  From 2014 to October 2023, an expenditure of Rs 19,043 crore has been made to complete all the ongoing Metro projects in the city.