Half an hour later, Yan Fei had finally dug forward 10 meters. According to the display on the 3D map, just beyond the left stone wall was a corner of the Underground Gold Vault's wall. It was now 7 PM in New York local time, and since Yan Fei had entered the Subway Tunnel, he had been working non-stop underground for two hours. Even with his formidable strength, he was beginning to feel some fatigue.
Yan Fei took out the black sphere from the Universal Space and used the Mysterious Energy within it to recover from the tiredness. He rested on the spot for a while, then proceeded to dig towards the direction of the Underground Gold Vault's wall. Ten minutes later, Yan Fei had dug through the softer rock layer near the vault and encountered the hardest rock layer within. The 3D map showed that this hard rock layer was five meters thick, and beyond it was the Underground Gold Vault's massive reinforced concrete structure.
