An apparatus is disclosed which may serve as a target for calibrating a camera. The apparatus includes a hollow body having an interior surface, an exterior surface and at least one window formed in the hollow body through which the interior surface is visible. A plurality of distinguishable fiducial markers are arranged in a predetermined pattern along the interior and exterior surface of the hollow body. The fiducial markers can be distinguishable such that, for any given image of the target captured by a camera, there is only one position, rotation, distortion value, and focal length for the camera of interest.