In the lesson "Which witch is which" there is the following comparisson:
"Small towns are safer than big towns" --> 小さいまちは、大きいまちよりあんぜんです。
If I remember well then 大きい is a な adjective, so I expected: 大きなまち.
So my question is, why is the な not needed in this case? Is it because it is about big cities in general instead of a particular big city?
or is it something that I have already learned in an earlier lesson but forgotten all about?