Complex sentence: Planned, designed and founded by Lama Lhatsun Chempo in 1705, it is one of the oldest and premier monasteries of Sikkim, also the most famous in west Sikkim.
Split into simpler sentences: Planned, designed and founded by Lama Lhatsun Chempo in 1705, it is one of the oldest and premier monasteries of Sikkim. It is not only one of the oldest monasteries of Sikkim but also the most famous in west Sikkim.