Cerro Pachon is located 10 kilometers southeast of the Cerro Tololo Inter-American Observatory, at 2715m in the foothills of the Chilean Andes. The mountaintop is exceedingly dry, making it suitable for infrared observations. The air overhead is very stable, yielding excellent seeing. During the summer months, Cerro Pachon is often above the haze layer that can envelop lower altitudes.
The Gemini structure is located at the high point of the Pachon ridgeline. The north face is very steep, with cliffs along most of the length of the ridge. The enclosure is located on the cliff side, with the support facility directly to the south. There is now a well-developed graded earth road from Cerro Tololo to the Gemini site on Cerro Pachon, and other developments are currently underway.