The 754.40 square kms. of the Great Himalayan national park ( GHNP) offer some of the most enchanting mountain trekking in the Himalayas.The GHNP has developed trails and camping sites and franchised a local CBO-SAHARA-to organize the men and materials for the trekkers. the Tirthan and sainj are two of the four rivers that flow through the park, and this trek takes one from the valley of the Tirthan,over the supakhani jogni to the Sainj valley. Trek begins from a small village called Gushaini on banks of the Tirthan, one of the last few rivers in Himachal which still have trout.Follow Tirthan upstream for 8kms to Rolla(2100mts.) which has a forest hut.On day two track leaves the Tirthan and climbs to the north-east cresting two ridge lines, Rakhundi top(3622mts.) andGhumtarao(3500mts.)which is a verdant pasture and camping site. Day three is over alpine pastures dotted with juniper and dwarf rhododendron among which one can spot musk deer. Night camp is at Dhela thatch(3737mts.) which has a large trekker's hut,flowing water and magnificent views of the khandedar massif.This is prime monal and western tragopan habitat,On day four one descends through dense forests of spruce, brown oak, fir, cedar and then broad leafs-walnut, jamun, maple and horse chest-nut-to shakti where one crosses the sainj river.Shakti(2200mts) has a fine trekker's camp with toilets and piped water, on the banks of the river in the middle of a thick green grove of sea-buck thorn. final day's trek is the longest-21kms-but almost level along and down the sainj, most of it through the sainj wildlife sanctuary.one can pick up amazing driftwood on the river bank.About five hours to Neulli- the roadhead- where one can get taxis or buses for aut on the main NH 21 to kullu. permission for trekking in the GHNP has to be obtained from the director GHNP at shamshi.