I am planning to go to Inner Mongolia, an autonomous region of China, next week.

I have been to Outer Mongolia.

I have been to Chicago.

The Mesolithic is the era between the Paleolithic and the Neolithic.

The Bronze Age was an important period in human history.

The Azuchi-Momoyama period was a very important time in Japanese history.

The Azuchi-Momoyama period, also known as the Oda-Nobunaga period, was a very important time in Japanese history.

The Neolithic was an important period in human history.

The Paleolithic is the first era of human history.