The correct answer is Rohtang.

• Atal Tunnel passes through the Rohtang pass.

• On October 3, Prime Minister Narendra Modi inaugurated ‘Atal Tunnel’ at Rohtang in Himachal Pradesh.
• It is the world’s longest road tunnel at an altitude of 3,000 metres from the sea level.
• The 9.02-km-long tunnel was built by the Border Roads Organisation and connects Manali to Lahaul-Spiti Valley.
• It will provide all-weather connectivity to the landlocked district, which remains closed for nearly six months in a year due to the Rohtang Pass being completely snow-clad between November and April.

• The tunnel reduces the road distance between Manali and Leh by 46 km and the time by four to five hours.
• It is a horseshoe-shaped, single-tube, double-lane tunnel with a roadway of 8 m.
• The tunnel has been designed for traffic density of 3,000 cars a day and 1,500 trucks a day at a maximum speed of 80 kmph.
• The Union Cabinet in 2019 decided to name it ‘Atal Tunnel’ to honour the contribution made by the former Prime Minister Atal Bihari Vajpayee.
• The foundation stone for the tunnel was laid by UPA chairperson Sonia Gandhi on June 28, 2010.
• Important railway tunnel:
  • The longest railway tunnel in the world is the Gotthard base tunnel in Switzerland.
  • Seikan Tunnel is 53 Km long and situated in Japan.
  • Yulhyeon Tunnel is 50 Km long and situated in South Korea.
  • Channel Tunnel is situated on the English Channel on Dover strait.