From the Jungfraujoch station (3454 m) exit through the Sphinx tunnel. From here, to avoid the largest crevasses, descend initially south-west over the Jungfraufirn (glacier) to reach the first, flatter glacial depression. From here turn south-east into the next hollow at about 3200 m. Continue south-south-east towards the lower flanks of the Trugberg and onto ​​the flatter part of the Jungfraufirn. Then while maintaining a safe distance keep approximately parallel to the Trugberg until near the glacial junction at P. 2763, where the Jungfraufirn and the Ewigschneefäld come together. The small lake at P. 2763 is bypassed to the south. Continue on the left (E) side of the stream, which flows from the small lake, climb slightly towards the Ewigschneefäld but essentially countour round to its southern edge and then on to the south foot of the Grünegg. 2 to 2hrs 30mins. A lake is not always present at P. 2763; the water may have found a sub-surface channel, hence the wide and deep channel leading from the lake will also be gone. In this case you can cross further south (more directly) towards the foot of the Grünegg.