In June, as usual, I traveled to Bolivia to team up with New Zealand expat Gregg Beisly, who has been based in the country for the last five years. On June 2 we acclimatized by making the first recorded ascent of Pico 5,540m (Bolivian IGM 5946 III map) from the 4,700m low camp for Chearoco and Chachacomani. A better approach would be from Chearoco high camp at 5,200m. From there, head southwest to an obvious group of lakes, then climb west over a moraine field to the north ridge of Pico 5,540m. The last 200m along this ridge comprise a rocky crest leading to an elegant summit on a large, imposing gendarme (PD+ 4).

On the 4th we climbed Chachacomani (6,048m) from a high camp at 5,400m, and then the following week, with the intention of completing all the 6,000m peaks in Bolivia, traveled to South Lipez and climbed the volcano Uturunku (6,048m), near the Chile/Argentina border. We now had only two 6,000ers left to climb to complete the set, but decided to forego these in order to attempt the highly coveted Grand Traverse of the Illimani Massif. This traverse crosses all five 6,000m summits of Illimani, and although attempted on a number of occasions, from south to north or vice versa, only three complete traverses have been recorded, each taking between four and six days. The shorter three-peaks traverse (north-central-main) is now done regularly, though there are different accepted start and finish points. In 2015, Roberto Gomez, a guide from La Paz, and Andy Polosky, a German guide living in the USA, completed the three-peaks traverse in a single push of less than 19 hours.

On June 16, with Andy Baker (U.S.), Gregg and I set off at 6:30 a.m. from Mina Aguila (4,800m), just above Laguna Tijrac Khota on the northern flank of Illimani. We walked over moraine to reach an easy snow gully that gave access to the northwest ridge at 5,800m. We followed this ridge over a series of tops to Pico del Indio (6,109m), then climbed along a complex, undulating, heavily corniced ridge to a col, then upward over a series of tops to Pico del Norte (6,403m), which we reached at 6:45 p.m. We dropped down the southeast ridge and at 7:30 p.m. reached a col at 6,250m, where we made an open bivouac.

The following day we climbed the north ridge of Pico Central (6,362m), then dropped to the col between Picos Central and Sur, from which we descended east on a glacier with soft snow to climb Pico Layka Khollu (6,159m). We retraced our steps to the col and climbed Pico Sur (6,438m), then descended the normal route west to Nido de Condores, which we reached at 5:30 p.m. We continued down and off the mountain after an overall climbing time of 22 hours.

The complex and stunning summit ridge of the Illimani massif runs for 13km, all over 6,000m, making it an Andean super-classic. Conditions were generally favorable, although early-season soft snow slowed us down, and often large cornices required sustained crab-climbing on either the east or west side of the ridge. Overnight temperatures dropped to -20°C.

The key to a successful crossing is adequate acclimatization, as developing altitude sickness once past Pico del Indio would present real difficulties—there is no easy way out from here without climbing over 6,000m. After two weeks at altitude I still found it extremely hard going. If you don't get through this section in a day, it will require sleeping at well over 6,000m. There is little chance of rescue here and a real risk of frostbite, due to prolonged exposure to altitude and wind.

This was definitely one of the highlights of my more than 20 years of climbing.

Erik Monasterio, New Zealand

Editor's note: The first recorded five-peak traverse was made in 1979 by Anton and Ria Putz, and the second in 1997 by Bernard Francou, Jean-Emmanuel Sicart, and Patrick Wagnon. Both teams climbed from south to north. In August 1998, Yossi Brain, Peter Grosset (both U.K.), and Alesandro Bianchi and Marcello Sanguineti (both Italian) made the first north-to-south crossing. They chose to climb Pico Layka Khollu after Pico Sur and then continue south down the long glacier, from the end of which downclimbing and one rappel gave access to scree slopes, abandoned mine buildings, and eventually Cohoni.