Pickup in the morning from Dehradun and reach Dhaula (~ 1550m, 5100 ft) . Distance around 200 Km and can take up to 12 hours with lunch break in between. The road is one of the most scenic in Garhwal region while we go up to the classy hill station of Mussorie at the beginning, turquoise Yamuna river in the middle and conifer forests and meandering Tons river at the later half of the journey. The major points are Mussorie, Yamuna Pool, Damta, Nawgaon, Purola, Mori and Netwar. Mori is the last place where you get a guaranteed mobile network! From Netwar onward we are inside Govind National Park area and at the Forest Check Post entries are made. We cross the Tons River and enter into Rupin valley.  Dhaula is a small village with handful of homes and few home-stays for shelter. We camp for the night beside Rupin.

Our trek starts today. From campsite we take the wide trail and cross the Rupin for the first time. (Hence onward we will cross Rupin on few occasions till the base of Waterfall) . After crossing the bridge Rupin stays for the day on our right side. The walk is gentle along the river valley with very low gradient. Rupin runs in the gorge some 500 ft below. One moderate climb of 30 mins takes us to the village of Datadhar. Then we traverse and encircle the mountains for couple of hours gently along Rupin to reach the village of Sewa (~ 2000m, 6550ft). The village is a small one with a tea shop and a small lodge.  Wooden crafted temple in the village depicts the influence of Kinnaur culture. The Distance is 10 Km and may take up to 6 hours. There is a nice camping ground just another kilometer after the village on the bank of Rupin.  After crossing a short jungle stretch we descent to the river bed  and cross a side stream called Aligad. The bridge marks the boundary of Uttarakhand and Himachal. The campsite of Aligad (~ 1900m/6230 ft) is on the true right of Rupin in the state of Himachal Pradesh. It may take up to 6 ours.

We start in the morning on the stoned trail and reach the suspension bridge at Seema. The trail straight ahead goes to Ruinsara Tal and further to Bali Pass or Dhumdharkandi Pass. Cross the Tamosa river and climb up to reach the trail which is going along the river upstream. From now onward the river will be on our right (“True Right” of the river) and we gradually go up to reach a vast green expanse which is a huge clearing for farming by the people of Osla. From here the peaks facing north and north east opens up and the views of Banderpunch group and Swargarohini group are breathtaking along with Black Peak (Kalanag). We gradually skirt the mountain for another hour to reach the base of the steady climb to Kalkatti Dhar. From here we can see the Ruinsara valley takes a right turn , while we take a left turn. Har Ki Dun Nallah and Ruinsara Nallah meets below Kalkatti Dhar to form Tamosa river. It is normally windy while we climb to Kalkatti Dhar. After reaching the the highest point on the shoulder of the mountain we turn left and gradually go down. First time after Seema we again enter into the forest and descend steadily to a side stream. In winter the waterfall remains frozen. This is a good place to have lunch. From here we gradually climb in to a forest canopy of Silver Fir , Cedar and Oak. Crossing the forest we enter in to the wider valley with occasional Birch ( Bhurja Patra in Hindi) and Rhododendrons. The valley is teemed with bird life. Buntings, Flycatchers and Mountain Fiches are abundant. Himalayan Langur and Blue Sheep are common in this valley. There are reported sightings of elusive Snow Leopard in this region. Now the river bed is almost at the same level and Har Ki Dun valley approaches. The camping ground is near the river and several tents can be pitched. Walk another 10 mins to cross the Har Ki Dun Nallah over a small wooden bridge. Forest Rest house (FRH) is a minutes walk from here. GMVN TRH is another 10 mins ahead. It is mandatory in winter to book in advance for any of these huts. Caretaker only comes along with the keys for a prior booking. During summer food is available in GMVN TRH. There are two rooms at FRH and one dormitory at GMVN which can be booked. It is better to come with own tent and provisions in season to avoid any hassle. Total distance is 11 Km and may take 5/6 hours. Average height of the valley is ~ 3500 m/11500 ft. Camp for the night.

Wake up early in the morning to see the sunrise on Swargarohini group of peaks. Changing colour is magnificent to watch and unforgettable. The Forest Rest House (FRH) is located some what centrally in this vast expanse of the valley.  Heading straight from FRH is Har Ki Dun peak. On the right towering Swargarohini and to the left is Hata peak. Two streams are coming from two different directions, one from Jaundar glacier and other from Borasu pass watershed to Har Ki Dun and forming the Har Ki Dun Nallah. Har Ki Dun is a big enough valley sitting in the middle with forking of trails in different directions. Treeline recedes here in all directions. Today is an exploration day amidst snow or simply one can sit back at the campsite and relax while sipping a cup of coffee. After breakfast one can either go to explore the Jaundar glacier or to Maninda Tal area, which are on different directions. The snout of Janudar glacier is 8 Km from Har Ki Dun. The trail is not defined and on snow, boulder and moraine, involving descent and ascent. It is pretty difficult to reach the snout of the glacier and return to the campsite in a single push. A camping is required in between. It is advisable to venture and advance in this direction only till noon and retrace back by 3 pm. On the other hand, Maninda Tal is about 2 hours walk from Har Ki Dun and is in the route towards Borasu Pass trail which connects this valley to Baspa valley in Kinnaur, Himachal Pradesh. The area is a shallow formation of clogged water resulting from a flattened bed of the stream. The valley heading upward looks splendid from here. Lammergeier and Himalayan Griffons encircle the valley surrounded by rocky cliffs. Pug marks of Snow Leopard following a flock of Bharal (Blue Sheep) is common. Return to Har Ki Dun by lunch time and take the hot lunch prepared freshly. From the FRH cross the wooden bridge on the Har Ki Dun Nallah walk toward the camping ground in the afternoon. Kedarkanta peak is clearly visible and the highest point in this direction. Sunset is mesmerising , reflecting the last rays of sun on Har Ki Dun Nallah and peak. Changing golden hue makes any trekker a spellbound spectator. It is a good idea to collect firewood to setup a fire in the night. This is already a fragile ecosystem, so ONLY collect branches and twigs which are already fallen from the trees. The FRH has a fireplace inside. Nights are pretty cold here and the temperature can plummet to -10 deg C outside the night in winters. Night stay in tent.

Today after breakfast we start our return journey toward Seema. It is a gentle descent along downstream till we reach the waterfall which remains frozen in winter. From here we climb up to Kalkatti Dhar and descend gradually to the vast crop field. Approaching the Seema bridge, we take the trail straight heading toward the village Osla, instead of directly going down to Seema. It is a memorable experience to visit a village like Osla, nestled on the lap of mountain. The houses are mostly build of wooden structure with slate as the roof. Houses are two storied, lower being the cattle shelter and firewood/fodder store, upper being the residence of the family. Though few satellite TV dishes  are present on top of few houses but the village lacks  very basic facilities.  A satellite phone is available to connect to the outer world. One can make a phone call to home by paying nominal charge, if a connection is available. The village is spread along the slope of the mountain and a temple is the heart of the village. Wood crafted temple is more than a century old. It is a legend that Duryodhan, the eldest brother of the Kauravas is worshipped in this temple. The deity of the temple resides at different temples of the villages of this valley, turn by turn. The rule being same across the Himalaya, summer is higher, and winter is lower. It is a chance to meet local children and people, knowing their livelihood, custom and culture, social structure. It is worthwhile to spend some time with joyful kids in the village. After spending some time in the village we take the trail down toward the Seema bridge and by crossing the suspension bridge we reach Seema. Night accommodation in tent.

We retrace our trail back to Taluka. From here take the car to reach the trek end point Sankri. Night stay in lodge/homestay.

In the morning we start our return journey and reach Dehradun by 7 pm. Trip ends here.

P.S.: Distances and altitudes are approximate and may not be exact.