Suzhou,( )we spent last spring,is one of the most beautiful

Suzhou,( )we spent last spring,is one of the most beautiful cities in china?
这是一道定语从句的题目,有四个选项,where,which,that,in which,括号内填哪个好?
我的教辅上也选which,可我认为缺少地点状语，应选where，请讲一下原因