Abstract: A method and arrangement for destroying tunnels. A subterraneous, vertical shaft is excavated until a tunnel preventing depth. After liquid is introduced to the shaft, a shaft liner is penetrable by the introduced liquid when a tunnel is present in the vicinity of said shaft, due to the considerably larger pressure of the introduced liquid relative to the bearing capacity of soil interposed between the tunnel and shaft. The tunnel is then flooded and destroyed following passage of the liquid through the liner. A system for detecting and destroying tunnels in the proximity of a security-sensitive facility comprises a hollow member anchored to the upper soil surface adjoining each shaft, a sensor having a unique address mounted on a corresponding hollow member for generating an electrical output when the liquid level has been reduced more than a predetermined level, and a computer in data communication with each of the sensors.