Which is the largest Monastery in India?

Concept: India's Himalayan belt — Arunachal Pradesh, Ladakh/Zanskar, and Sikkim — hosts many historic Tibetan Buddhist monasteries (gompas). Claims about which one is the 'largest' are judged by built-up area and monk capacity, and must be anchored to verified sources (government tourism records, encyclopedic references) rather than fame or antiquity alone.

Application: Tawang Monastery in Arunachal Pradesh was founded in 1680-81 by Merak Lama Lodre Gyatso on the instruction of the 5th Dalai Lama. It is documented (Wikipedia; the Ministry of Tourism's Incredible India portal) as the largest monastery in India by built-up area and monk capacity, and the second-largest in the world after the Potala Palace in Lhasa, Tibet.

• Thiksey Monastery, Ladakh — architecturally striking and often called a 'mini Potala' for its resemblance to the Potala Palace, but its built-up area and monk capacity are smaller than the largest monastery in Arunachal Pradesh.

• Phuktal Monastery, Zanskar — distinctive for being built around a cliffside cave and reachable only on foot or by mule, but that uniqueness is about its setting and accessibility, not overall scale — it is a compact monastic settlement.

• Rumtek Monastery, Sikkim — significant as the principal seat-in-exile of the Karmapa and the Karma Kagyu lineage, and one of the largest monasteries in Sikkim, but at the national level its built-up area and monk strength are smaller than the largest monastery in Arunachal Pradesh.

Hence, among the given options, the monastery in Arunachal Pradesh is the largest monastery in India.