Looks like taxiways leading to a cliff for underground aircraft storage.
There was a plan to do this at Ta Qali but it was found to be impractical, so I'd guess it was the 'secret' airbase somewhere north of Groom Lake where Bob Lazar was briefly employed.
He maintained we was flown from Vegas to Groom Lake by one of the Janet flights, then was transported further into the desert in a bus with blacked out windows, to where he was employed on 'back engineering' flying saucers using 'compartmented information'.