Watch Secrets of the Underground Season HD Full Free on solarmovie.do. Watch Secrets of the Underground tv series online free. Using cutting-edge technologies such as ground penetrating radar (GPR), LIDAR (Light Detection and R...Using cutting-edge technologies such as ground penetrating radar (GPR), LIDAR (Light Detection and Ranging), and 3-D imaging, scientists research fascinating underworlds of secret tunnel networks, ancient structures, and bizarre geological occurrences that offer glimpses into our history.