An underground barrier for detecting underground hollows, comprising: a drilling rig； at least one drillstring, a proximal end of the drillstring, fitted on the drilling rig, the drillstring capable of drilling a borehole into the ground； a directional drilling unit, fitted on a distal end of the drillstring, capable of steering the drillstring in a desired path； a sensor unit, fitted on the distal end of the drillstring, capable of mapping the ground and hollows around the drillstring； and a control station； the control station configured to preform one or more of the following: control, the directional drilling unit to steer the drillstring in a desired path； receive, mapping data of the ground around the drillstring from the sensor unit； analyze, the mapping data received to detect underground hollows； and display, to a user of the system, using a user interface, the mapping data and the underground hollows.
