Abstract: A tunnel is constructed by progressively cutting away a predetermined depth of rock from a face using rotary diamond saws. Slots are cut into the face (12) at an acute angle to the face such that first slots intersect second slots to detach blocks from the face. In one embodiment, the cutter (29) is mounted on a slide which can traverse an elongate guide 26. The guide is carried on an arm (24) which can swivel about its own longitudinal axis. A series of angularly spaced slots are cut into the face through 360.degree. with alternate slots being cut at opposite acute angles to the face so that they intersect. A cylindrical tunnel is produced.