Geologically, Illimani is composed primarily of granodiorite, intruded during the Cenozoic era into the sedimentary rock, which forms the bulk of the Cordillera Real.

[4] Illimani is quite visible from the cities of El Alto and La Paz, and is their major landmark.

In July 2010 German climber Florian Hill and long-time Bolivian resident Robert Rauch climbed a new route on the 'South Face', completing most of the 1700m of ascent in 21 hours.

Deliver Me (WI 6 and M6+) appears to climb the gable-end of the South West Ridge, a very steep wall threatened by large broken seracs.

[7] In 1973 Pierre Dedieu, French, and Ernesto Sánchez, Bolivia's best climber, perished climbing Illimani in August.

[9] US Major Kenneth R. Miller, US Colonel Paul Bruce Kappelman, and Bolivian guide Vincente Perez died in a climbing accident on June 7, 2003.