According to The Print, satellite imagery identified a deeply buried hardened target (DBHT) under construction outside the town of Ngari, also known as Shiquanhe in Mandarin.
Construction started in December 2016, about six months before the 2017 China–India border standoff near the India-China-Bhutan tri-junction in the east.
The Print, specified that special personnel are being used instead of locals, to maintain secrecy and security of the project.
The UGF appears to have four large tunnel entrances and three small ones; all have hardened entrances with reinforced concrete. Judging by the images, the openings would soon be covered with other material to withstand a direct military strike.