He was spending time alone in the smoke tower.

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.

This old tunnel was once used in a mine.

This old tunnel was once a key point of transportation.

This old tunnel was once a key point of transportation.

My son is learning karate.

The gynecologist checks the health of the vagina.