Assam to the south and Arunachel Pradesh to the east. The country within these border forms a giant staircase, from the grassy floodplains and reverie forests in the south through semi tropical and alpine forests to some of the highest unclimbed Himalayan peaks on earth. Most of the population continues to live in small, isolated farms and hamlets surrounded by terraced fields of rice and cereal crops. At higher altitudes, in isolated valleys, people still live in tents woven from yak-hair, spending part of the year in alpine pastures, grazing their livestock. Much of Bhutan is still covered in thick forest, which sustains a wealth of plant and bird life. Above the tree line the country is wild and rugged; the mountains are largely unexplored and offer some of the best trekking in the Himalayas.