Borehole information is widely used for many purposes since the data provides essential and accurate geological information of underground and surface conditions. The borehole data is generally provided in the form of boring logs which contains boring data of a single borehole so a lot of boring logs are required to produce further information about a target area. We developed application software for the iPad to enable a user to look into the underground from the surface using borehole information and augmented reality techniques. The borehole data from a remote data server or internal storage of the iPad is processed internally and then overlaid on a camera screen or 2-dimensional map so the user can navigate the borehole data visually. Various geological and geotechnical information (i.e. USCS rating and explanation of each layer, bed rock type, N-value obtained from standard penetration test, groundwater level) as well as positional information (i.e., depth, coordinate, altitude) of the underground can be identified by touching the searched borehole data. The user also can modify existing data or add a new borehole in the field. A field survey was also carried out using more than 100,000 borehole data to validate the accuracy and reliability of the system.