It's one of the best places _I have ever been. It's the most beautiful place __I have ever visited

It's one of the best places _I have ever been.It's the most beautiful place __I have ever visited
为什么第一个空填where,而第二个空填that?求详解!
这涉及定语从句中的先行词在从句中充当什么句子成份的问题.要正确选择关系代词、副词,首先,你要判断先行词在从句中当什么成份,如果先行词在从句中当宾语或主语,那么,你就可以选择可以在从句中当宾语的关系代词,如：whom,that,which等,如果先行词在从句中不是当宾语,而是时间状语,地点状语,那么,你就应该选择在从句中可以充当状语的关系副词,如：where,when等.特别要注意的是：先行词是表示时间和地点的词,不搞清楚他们在从句中所充当的句子成份,很容易出错.
It's one of the best places __________I have ever been.
本句话中的先行词是表示地点的词：places,第一感觉是地点,按常规,选择where,验证是否正确,就要看places在从句I have ever been中,起什么语法作用.这句话可以理解成：I have been to the places.places 在从句中是表示地点,去过的地方,是状语,所以用where.
It's the most beautiful place _________I have ever visited
同样,要找出这句话中先行词places在从句I have ever visited 中充当的句子成份.很显然the places在这句话中是当visited的宾语,即：I have ever visited the places.所以选择which 或that,
但这句话中前面有*,所以只能选择that.