Arunachal Pradesh remains one of India's least-visited states relative to what it offers, mostly because getting there takes real planning — permits, road time, and weather all have to line up before the trip can happen at all.
Indian citizens need an Inner Line Permit to enter Arunachal Pradesh, applied for online through the state's e-ILP portal. It isn't a same-day formality, so it's worth sorting at least a couple of weeks before travel rather than assuming it can be arranged on arrival.
The nearest airports are Guwahati and Tezpur, and from either, Tawang is a genuine mountain drive — roughly 500km that takes twelve to fifteen hours, usually broken into two days via Bomdila and Dirang rather than done in one push.
Tawang Monastery, the largest in India and the second-largest in the world after Lhasa's, is home to several hundred monks and a centuries-old library of Buddhist manuscripts. Mornings are the quietest time to visit, before the day's tour groups arrive.
Sela Pass, at over 13,700 feet, is usually snow-covered well into spring and is the dramatic midpoint of the road to Tawang. Bumla Pass, right on the India-China border, needs separate prior clearance and isn't guaranteed to be open on any given day, so it's better treated as a bonus than as the centrepiece of the plan. Given how weather-dependent the roads are, we build slack days into any Arunachal itinerary rather than a tight point-to-point schedule, and handle the ILP paperwork as part of booking.