The 8.8 km-long Himalayan tunnel, hailed as an engineering wonder that is coming up under the Indian Army's road building wing, will be inaugurated by Congress president Sonia Gandhi, giving wing to her husband and late prime minister Rajiv Gandhi's dream.
Located in Himachal Pradesh, the tunnel is expected to be ready by 2015 and will serve as a nerve centre for the Indian Army to carry supplies to Ladakh.
"It will be much longer than the present longest tunnels anywhere in the world at altitudes over 2,500 m. The nearest in comparison to the Rohtang Tunnel is the Anzob in Tajikistan which is five kilometres long at an altitude of 3,372 m," said a spokesperson of the defence ministry that is constructing the "engineering marvel".
It was a dream of Sonia Gandhi's late husband Rajiv Gandhi, who had conceived it 26 years ago. She will fly to Rohtang Pass in the Pir Panjal range of mountains, 51 km from the hill town of Manali, to lay the foundation stone of the Rs.1,495 crore tunnel.
Ladakh, a cold desert region, shares borders with China and Pakistan. The Kargil sector of the region was at the centre of the 1999 India-Pakistan military conflict.
The over eight kilometer long mountainous stretch where the tunnel is being built otherwise remains snowbound, cutting off the tribal Lahaul-Spiti Valley in Himachal Pradesh and also the strategically vital Ladakh region from the rest of the country for over six months every year.
The tunnel will take over five years to complete and the ministry of defence says digging for the tunnel remains the most challenging task.
"The tunnel's design would be novel in many ways," said the defence ministry spokesperson.
Its distance and the "rarefied atmosphere" at the heights it is located at, the official said, make the tunnel a "landmark in the making".
"The tunnel would incorporate semi-transverse ventilation system," he said, boasting of large fans that would circulate air in and out throughout the tunnel length.
With a horseshoe shaped cross-section, the tunnel will be 11.25 m wide at road level. That means there will be ample room for two-way traffic travelling at a maximum speed of 80 kmph.
The Rohtang tunnel will have more to offer. It is expected to reduce the road distance to Ladakh by approximately 48 km and save travel time of about four hours.
"It will open up new vistas of trade and tourism and generate jobs for the benefit of the local population (in the Lahaul-Spiti valley)," said the official.
Defence Minister A.K. Antony, his deputy M.M. Pallam Raju, the chief ministers of Himachal Pradesh and Jammu and Kashmir - Prem Kumar Dhumal and Omar Abdullah - and Steel Minister Virbhadra Singh will be present at the inaugural ceremony.
The contract for the tunnel has been obtained by Austrian company Strabag and India's Afcons.
The longest road tunnel in India at present is the 2.8 km-long Jawahar Tunnel in Jammu and Kashmir with an altitude of 2,209 m.