I live in Vietnam and it is indeed as beautiful as you describe. It is a great pity that you missed Ninh Binh, which I consider to be the finest destination in the entire country. It is only 90 minutes from Hanoi and is truly wonderful. You can read about it in my blog here: http://www.inseasia.com/2017/04/magnificent-ninh-binh-trang-an-grottoes/