this is the best place __I have ever visited all my life

that 前面是best place 表示特指某一地点,因为最好的地方是独一无二的,所以只能用that,不能用where.
希望我的回答能对你有帮助
如果还有问题,可以问我,^_^就这道题，能给我具体解释吗，谢谢where在前面是泛指时可以，比如this is the house where I used live in。但是如果是用best，就要说this is the best house that I have lived in。