And, in the very heart of Saigon is the Notre Dame Cathedral. The French played a very important and influential part in the development of language and culture in Vietnam during the 1700 and 1800's...A French priest is responsible for giving the language a written form - using Roman characters for letters. Though heavily influenced also by the Chinese, the Vietnamese have a written language that looks very European. However, it does not sound European and has five tones for many of its words.