Running from Assam to Uttar Pradesh covering a distance of 1,800 km, the Biswanath Chariyali- Agra line is a part of Power Grid's Northeast to Northern / Western Interconnector-1 project to transfer surplus power from the North-Eastern region to the power deficit northern and western regions of the country. We built 166 km of 800 kV (Hexa bundle) HVDC Biswanath Chariyali, Tangla transmission line and approximately 74 km of 110 / 132 kV (twin bundle) Earth Electrode line from Biswanath Chariiyali & Thagiabari. Being one-of-a-kind in Asia, the HVDC lines posed challenges of huge complexity and dimension with towers weighing between 30 to 124 T and varied foundation pits necessitating geotechnical innovations.