Long tunnels with high rock cover have become one of the important infrastructures in recent transportation projects in Taiwan and have been considered as a key factor controlling the over all construction schedule. Cases in this island and around the world indicated that difficult ground conditions can not be avoided in any underground construction and should not be overlooked during planning stage, design stage and construction stage. This paper introduces several cases regarding the unfavorable ground conditions encountered in long tunnels with high rock cover and is followed by a brief discussion on the future geological exploration of long tunnel.