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 Paleogene period was a very important time in the history of the Earth.

He starts talking about himself at every opportunity, causing trouble for the people around him.

The Paleolithic is the first era of human history.

The Bronze Age was an important period in human history.

The Neolithic was an important period in human history.

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

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