an insurgency spanning decades, including occasional massacres such as the 1980 Mandai massacre. This gradually abated following the establishment of a tribal autonomous district council and the use of strategic counter-insurgency operations. Tripura remains peaceful, as of 2016. In retaliation of the communal violence against the Hindu minority in neighboring Bangladesh, mosques in several areas in Tripura were attacked from 19 to 26 October 2021. Geography Tripura is a landlocked state in North East India, where the seven contiguous states – Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura – are collectively known as the Seven Sister States. Spread over , Tripura is the third-smallest among the 29 states in the country, behind Goa and Sikkim. It extends from 22°56'N to 24°32'N, and 91°09'E to 92°20'E. Its maximum extent measures about from north to south, and east to west. Tripura is bordered by the country of Bangladesh to the west, north and south; and the Indian states of Assam to the north east; and Mizoram to the east. It is accessible by national highways passing through the Karimganj district of Assam and Mamit district of Mizoram. Topography The physiography is characterised by hill ranges, valleys and plains. The state has five anticlinal ranges of hills running north to south, from Boromura in the west, through Atharamura, Longtharai and Shakhan, to the Jampui Hills in the east. The intervening synclines are the Agartala–Udaipur, Khowai–Teliamura, Kamalpur–Ambasa, Kailasahar–Manu and Dharmanagar–Kanchanpur valleys. At an altitude of , Betling Shib in the Jampui range is the state's highest point. The small isolated hillocks interspersed throughout the state are known as tillas, and the narrow fertile alluvial valleys, mostly present in the west, are called Doóng/lungas. A number of rivers originate in the hills of Tripura and flow into Bangladesh. The Khowai, Dhalai, Manu, Juri and Longai flow towards the north; the Gumti to the west; and the Muhuri and Feni to the south west. The lithostratigraphy data published by the Geological Survey of India dates the rocks, on the geologic time scale, between the Oligocene epoch, approximately 34 to 23 million years ago, and the Holocene epoch, which started 12,000 years ago. The hills have red laterite soil that is porous. The flood plains and narrow valleys are overlain by alluvial soil, and those in the west and south constitute most of the agricultural land. According to the Bureau of Indian Standards, on a