Cities themselves are changing rapidly...是什么意思？

Cities themselves are changing rapidly...

城市自身在日新月异地变化。

cities

n. 城市( city的名词复数 )，全市居民，（由国王或女王授予特权，通常有大教堂的）特许市，（由政府授予特权的）特权市；

例句
Some cities are always going to be more advantaged.
一些城市总会有一些得天独厚的优势。

themselves

pron. 他[她，它]们自己，他们亲自，“himself”的复数，“herself”的复数；

例句
Most officers and men acquitted themselves well throughout the action.
大多数军官及士兵在整个战斗中表现出色。

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

changing

n. 替换，变换，转换，变化；

例句
Some animal and plant species cannot accommodate to the rapidly changing conditions...
某些种类的动植物不能适应迅速变化的环境。

rapidly

adv. 很快地，迅速地，立即；

例句
He had discovered politics and was rapidly becoming absorbed by it...
他接触到了政治并且迅速地对它着了迷。