China builds world's longest underwater high-speed rail tunnel
Image Credit: shortpedia
You can reach the Zhoushan group of islands in Zhejiang province by car over a bridge or by air, which is quite popular with tourists. The undersea tunnel is being built and on completion, trains traveling at 250 km per hour will be able to travel from Ningbo to Zhoushan in just 30 mins, which currently takes thrice the time. AI management system will be used during the construction and there is zero contact remote supervision.