New Delhi, March 19 -- Delhi Metro Rail Corporation (DMRC) has successfully completed tunnelling at the deepest underground section of Phase-IV with a tunnel breakthrough at the IGNOU Station site (from Chhatarpur Mandir) on the Aerocity-Tughlakabad Corridor (Golden Line). This significant achievement took place in the presence of Delhi Chief Minister Rekha Gupta and Delhi Environment Minister Manjinder Singh Sirsa on Tuesday. The new tunnel has been built at an average depth of around 27 metres, one of Delhi Metro's deepest. The Delhi Metro noted that work on a parallel tunnel between Chhatarpur Mandir (Aerocity) and IGNOU (Tughlakabad) was completed in February. With the latest breakthrough, tunnelling for both up and down lines has now b...