Strenuous Grade Trekking is for trekkers with previous mountain walking experience. They ascend to altitudes of up to 5000m and engage some steep climbing where it is necessary to use ropes. At this level treks can be arranged for periods of 7-21 days. For a popular and stunning trek, with the possibility of staying in well-developed tea houses, the Annapurna circuit is a good option. A gradual ascent through a green river valley will lead you up to a number of high passes, where you will be reach the altitude of 5416m. This difficult trek will offer you a close insight into Tibetan culture. Another, as expected, popular trek with good tea house facilities, is the Mt. Everest Base camp trek. The goal of this trek speaks for itself, but in achieving it, you cross a glacier, see Mt.Everest and a whole diversity of high peaks and experience the amazing Sherpa culture. For a real adventure in wild and Makalu Base Camp the Makalu trek traverses many high passes before reaching the Base Camp at 5000m. The Tibetan plateau of Mustang is a wild, treeless desert. These last two treks are not very well established for tea house trek.