Abstract: A solar collecting system is incorporated into a natural rock mass having an upright face with a substantially direct exposure to the sun, for example a south facing granite cliff. A solar passage is formed in the rock mass to extend between an opening in the upright face of the rock mass and an internal collection area within the rock mass. One or more converging elements, for example solar converging lenses, are aligned with the solar passage and arranged to focus solar rays from the sun onto a target within the collection area. The target is in communication with a surrounding portion of the rock mass so as to be arranged to transfer heat from the target to the surrounding portion of the rock mass. A heat transfer fluid conduit may further be arranged to communicate a heat transfer fluid between the rock mass and an auxiliary device.