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CCAT will be a 25 m diameter, submillimeter-wave telescope. It will be located on Cerro Chajnantor in the Atacama Desert, near ALMA. CCAT will be an on-axis, Ritchey-Chretien design with an active primary to compensate gravitational deformations. The primary mirror will have 162 segments, each with similar to 0.5 x 0.5 m reflecting tiles on a similar to 2 x 2 m, insulated, carbon-fiber-reinforced-plastic subframe. CCAT will be equipped with wide-field, multi-color cameras and multi-object spectrometers at its Nasmyth foci. These instruments will cover all the atmospheric windows in the lambda = 0.2 to 2 mm range. The field of view at the Nasmyth foci will be 1 degrees, so CCAT will be able to support cameras with a few x 10(4) detectors (spaced 2 beamwidths) at lambda = 1 mm to a few x 10(6) detectors (spaced half a beamwidth) at lambda = 350 mu m. Single instruments of this size are probably impractical, so we will break the field into smaller pieces, with a separate sub-field camera for each piece. The cameras will require some relay optics to couple the fairly slow beam from the telescope to the detectors. A reflective relay for 1 degrees field of view is too large to be practical, so we plan to use a compact, cold, refractive relay in each sub-field camera.