Tay Ninh is in the northwest of Saigon and serves as the headquarters of Caodaism, one of Vietnam's most interesting indigenous religions. The area's dominant geographic feature is Black Lady Mountain and the eastern border is formed by the Saigon River. The Vam Co River flows from Cambodia through the western part of the province.
(http://www.indochinatravelservice.com/Travel/Vietnam/TayNinh/)