The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the expansion rate of the
Universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic
oscillations, and Type Ia supernovae. To perform the survey, the DES Collaboration is building the Dark Energy
Camera (DECam), a 3 square degree, 570 Megapixel CCD camera that will be mounted at the prime focus of the
Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. CCD production has finished, yielding
roughly twice the required 62 2kx4k detectors. The construction of DECam is nearly finished. Integration and
commissioning on a "telescope simulator" of the major hardware and software components, except for the optics,
recently concluded at Fermilab. Final assembly of the optical corrector has started at University College, London.
Some components have already been received at CTIO. "First-light" will be sometime in 2012. This oral presentation
concentrates on the technical challenges involved in building DECam (and how we overcame them), and the present
status of the instrument.