The Langtang region is an incredible place to visit and even today receives small numbers of trekkers compared to the Annapurna or Everest regions. Langtang means "follow the yak" and yaks there are. This region offers spectacular big mountain close up views and lots of variations in the route. There is something for just about everybody here. Trekkers can easily make it all the way to Kyanjin Gompa in the traditional tea house style and since the area is serviced by the road, relatively trouble free last minute planning is possible. Basically, all you have to do is catch one of the two daily buses to Dunche and just follow the trail. (As always, it is important to know where you are going and to be prepared but this is a very forgiving trek.)
The main trail departs from the roadhead (Dunche) and it takes the average person about 4 days to reach Kyanjin Gompa (12,000 ft). The wise traveler budgets at least 3 days to stay in Kyanjin as there are many short and long treks which can be taken from Kyanjin around the upper Langtang valley and boy, will you enjoy your time there. The most adventurous and prepared (food and tents) can launch a two or three day trip to the end of the valley (Langshisha Karka 13,400 ft) and peek at the Tibetan border and some more BIG mountains. But the area around Kyanjin is so beautiful and comfortable that not many people spend the night outside of the warm lodges in Kyanjin. The people in this area are very warm and friendly and the lodges vary from traditional (rustic) to a few more modern (solar shower) styles.
This area is also a National Park and therefore the 650 rupee rate must be paid by all tourist visiting the area. There are more checkpoints on this trek than any other trek (luckily most of them are on the road to Dunche). The checkposts are one way the army tries to patrol the national park.